* Automatic Transmission Identification
* Automatic Transmission Comparison
* Automatic Transmission Swapping
* Automatic Transmission Tuning
* Automatic Transmission Rebuilding

* Fundamentals

* Manual Transmission Identification
* Manual Transmission Comparison
* Manual Transmission Swapping
* Manual Transmission Tuning
* Manual Transmission Rebuilding

Submit corrections and additions to this information to The Olds FAQ Compiler.

Automatic Transmission Identification

On the RH side of the transmission, just above the pan, is an ID plate, about ½" in size. Gently wash off the grunge and look for the ID code painted on and stamped in as well.

It'll be of the form "OA-##-1234" where the 1st letter tells the car make: O is for Oldsmobile, B is for Buick, P is for Pontiac, etc., and the second letter denotes the application. Generally speaking, the higher the letter, the better. Some will have three letter designations, and the first letter can vary, such as L or J or F, etc.

The ## numbers is the year of the car: 68=1968, etc. No mystery here. The last 4 digits [1234 above] are the transmission unit number, not unlike the engine unit number found on the oil fill tube of 68-up engines.

Also, for 1968 and up applications, the VIN derivative will be stamped into the LH side of the transmission, between the two ribs and just above the pan. This will be the same number/letter combination that the engine received- see engine ID above for particulars.

Under GM's new transmission nomenclature, the first digit signifies the number of speeds, the second place is either L or T (for longitudinal - RWD or transverse-FWD, and no, they no longer make the longitudinal FWD Toro transmission), the next two are somehow related to the transmission's torque carrying capacity (higher is better), and the E designates electronic, as in computer controlled.

The electrical connectors on the TH-350C, TH-250C, and TH-200C are for the lockup torque converter clutch. Note that the 'C' suffix on the transmission model signifies it is a lockup torque converter model (i.e. TH-350: no lockup, TH-350C: lockup). The reverse light switch is part of the neutral safety switch assembly. The same switch is used to tell the ECM that the vehicle is in park/neutral as opposed to in gear (idle control).

GM uses two bellhouse patterns (on real cars, RWD, '64 or so to the end of the V-8, outside of the early hydramatics):

  1. Chevy. Looks like a mansard [barn] roof. Pointy at the top.
  2. Everyone else. Olds, Buick, Pontiac, Cadillac. Not pointy on top, kinda flat, with about 7" between the top 2 holes. I believe the indexing pins are common to both patterns, not quite sure on that.

The dual bolt patterns showed up when GM started to consolidate it's transmission operations and use "Chevy built" transmissions in BOP applications and "Hydramatic Built" transmissions in Chevy applicationas.

The 4L40-E, 5L40-E, and 3L40-E have replaceable bellhousings, but are mainly European applications. The 5L40-E is a 4L40-E with another gear in the middle. This transmission is being built exclusively for BMW for their 3 and 5 series vehicles. The 4L40-E is used in many including Opel, Cadillac Catera, Holden, and BMW M3, and some 3 and 5 series. Probably adaptable with some modifications as they both have replaceable bellhousings. Wouldn't take a lot of torque though.

Unicase transmissions aren't very common, in fact they fetch a decent price if you are actually looking to buy one from a tranny shop. I know all TH-2004R's that I have seen are unicase (makes you wonder why the 700's aren't), but I do know they started way earlier than 1980 - my original 1970 TH-350 is a unicase.

Actually - there never was a BOP TH-700-R4 (there is a BOP 4L60-E due to replaceable bellhousing - started in 1995). I believe the 4L80-E uses Chevy mainly but since it is sold to other customers, it might have another bolt pattern available.

An interesting website for GM engines and trannies is It has the spec sheets for all current models.

[ Thanks to Steve Ochs, Chris Witt, Joe Padavano, Stephen Hoover for this information. ]

Dual Path Hydramatic

Olds used the "Dual Range Hydramatic in 1954, and 53. I'm not sure how much earlier they used it though.

Olds used the "Dual Coupling Jetaway Hydramatic" (I just love thoes 50s names!) from 1956-1960. It came in two different flavors, with one model produced from 56-58, and the other from 59-60. I have a cutaway picture of both in a manual of mine, and the differences look minor.

That's right, a 4 speed auto! From the pics I have seen, it looks like it has 2 torque converters in it (thus the dual coupling designation). Why it does, I'm not really sure. The first model production run was from 1956 to 1959, the second model ran from 1959 to 1960. Differences were minimal. After they dropped the Jetaway in '60, they used a "Three Speed Hydramatic" until the Slim Jim Jetaway two speed appeared.

In 1961 the "Three Speed Hydramatic" was adopted, with a scaled down version used in the F-85. That tranny was used until 1963, when the 2 speed Jetaway was adopted. This transmission is not related to the "slip-n-slide Powerglide" though.

Pan Shape


[ Thanks to Scott Clark for this information. ]

Roto-Hydramatic (Slim Jim)

The Roto-hydromatic (Slim Jim) transmission was used at least 1961-1964.

Pan Shape


Power Glide

Pan Shape
|      |
|      \
|       |
|       |


Jetaway / TH-300

Pan Shape

Jetaway model and code numbers are stamped on the servo cover located at the right hand side of the tranmission. Some 1965 Jetaways have a green metal plate attached to the right side of the transmission. These numbers and letters appear as "YY" "XX" NNN", where YY is the last two digits of the model year, XX is the ID (found below), and NNN is the day the transmission was built.

Olds Jetaway ID's:
ID     Year(s)   Application
LJ     '65-'??   V-6 F-85 (33300, 33500 series)
MJ     '65-'??   LC 330 F-85 (33400, 33600 series), Cutlass F-85 Station
                 Wagon (33800 series)
MK     '65-'??   HC 330 Cutlass F-85 (33800 series), F-85 w/L-74
MT     '65-'??   LC, HC 330 Jetstar 88 (35200 series)
MU     '65-'??   HC 330 Jetstar 88 (35200 series) (L-74, L-76)


Switch Pitch ID
To identify a switch pitch transmission, look at the stator shaft. It has splines which are about half the usual length, and there is a large relief of the diameter of that shaft just behind the splines.


Pan Shape

Olds TH-325 ID's:
ID     Year(s)   Application
OE     '85       307 Toronado (VIN Y, F47)
OJ     '79       Toronado
OK     '79       Toronado (exc high alt)
OK     '85       350 diesel Toronado
OL     '79       Toronado (high alt)
OQ     '85       307 Toronado (VIN Y, F47)



Another easy way to tell the difference between a TH-200 and a TH-350 without crawling under the car is to look for a vacuum line running to the trans modulator. TH-350 has it, TH-200 does not. A fair number of the V-6 cars got the TH-350. The lighter V-6 saved enough weight that the heavier trans could be used. On the trans, the TH-200 and TH-250 have no vacuum modulator.

Pan Shape
A TH-350 pan is about 12" on a side, with one of the rear corners beveled off. The TH-200 is slightly smaller, closer to square.
|          |
|          |
|          |
|         /
|       /

Olds TH-350 ID's:
ID     Year(s)   Application
JB     '75       250 L-6 Omega
JE     '70-'??   1V 250 L-6 F-85, Cutlass (3100, 3500 series)
JE     '73-'74   1V 250 Omega
JE     '75       250 L-6 Cutlass
JG     '70-'??   2V 350 F-85, Cutlass, Supreme (3200, 3600, 4200 series)
JL     '70-'??   4V 350 F-85, Cutlass, Supreme (3200, 3600, 4200 series)
JO     '70-'??   4V 350 F-85, Cutlass w/W-31 (3200, 3600 series)
JM     '70-'??   350 Vista Cruiser (4800 series)
KA     '75       350 Omega
KD     '75       231 V-6 Starfire
KX     '75       231 V-6 Starfire (exc Calif)
LA     '73       4V 350 Omega, Cutlass
LA     '74       4V 350 Omega
LA     '75       260 Omega (exc Calif)
LC     '74       4V 350 Cutlass
LC     '75       350 Cutlas; 350 Wagons (Calif)
LE     '73       4V 350 Vista Cruiser
LE     '73       4V 350 Cutlass Wagons
LE     '75       350 Cutlass Wagons (exc Calif)
LH     '73       2V 350 Omega, Cutlass
LH     '75       260 Cutlass
NC     '75       260 Omega (Calif)


[ Thanks to Fred Nissen for this information. ]


A medium duty version of the TH-400. On the underside of the trans, right where the tail housing bolts up, the letters "TH-375" can usually be found cast into the trans housing.

Pan Shape
A TH-375 pan is the same shape and size as a TH-400.

Olds TH-375 ID's:
ID     Year(s)   Application
OA     '73       2V 350 88
OA     '74       4V 350 88
OA     '75       350 88
OB     '75       350 88 (Calif)
OE     '75       400 (Pontiac) 88 (exc Wagons)



A heavy duty version of the TH-350.

Pan Shape
The TH-375B pan is the same shape and size as the TH-350.



Pan Shape
The TH-400 is a bit larger and closer to square. The beveled rear corner is the clincher.
|            \
|             \
|              \
|             /
|            |
--\         /


Olds TH-400 ID's:
ID     Year(s)   Application
OA     '65       2V HC Jetstar 1, Dynamic, Delta 88, Starfire, 98
                 (35400-38600 series)
OA     '66       88, 98 big car
OA     '70       2V 350 w/K-30 Delta 88 (5400 series)
OB     '65       4V HC Jetstar 1, Dynamic, Delta 88, Starfire, 98
                 (35400-38600 series)
OB     '70       4V 455 Delta 88, Custom, Royale, 98 (5400-8600 series)
OC     '65       2V LC Jetstar 1, Dynamic, Delta 88, Starfire, 98
                 (35400-38600 series)
OC     '70       2V 455 Delta 88, Custom, Royale (5400-6600 series)
OC     '75       400 (Pontiac) 88, 98 Wagons
OD     '70       455 Cutlass, Supreme (3600, 4200 series)
OD     '72       4V 455 w/dual exhaust, exc. W-30
OD     '73-'74   4V 455 Cutlass
OD     '75       455 Cutlass
OE     '65       2V, 4V heavy duty Jetstar 1, Dynamic, Delta 88, Starfire, 98
                 (35400-38600 series)
OE     '74       4V 455 88 Wagons (Calif)
OF     '70       2V 350 w/o K-30 Delta 88 (5400 series)
OG     '67-'71   442, '69 W-32. Except W-30
OG     '70       4V 455 Cutlass Supreme, 442, W-32, except W-30 (4200,
                 4400 series)
WOG    '67       442, W-30
OH     '68       442, Hurst/Olds, Turnpike Cruiser
OK     '70       4V 455 w/K-30 Delta 88, Custom, Royale, 98 (5400-8600 series)
OK     '70       4V 455 Vista Cruiser (4800 series)
OK     '73-'74   4V 455 88, 98 w/dual exhaust
OK     '74       4V 455 88 Wagons
OK     '74       4V 455 88 Wagons (inc Hearse-Ambulance)
OL     '70       4V 455 Delta 88, Custom, Royale (5400-6600 series)
OL     '74       4V 455 88, 98 w/single exhaust (Calif)
OL     '75       455 88, 98 (Calif)
OM     '70       4V 455 w/W-34 Toronado (9400 series)
OR     '70       2V 455 w/K-30 Delta 88, Custom, Royale (5400-6600 series)
OR     '73-'74   4V 455 88, 98 w/single exhaust
OR     '75       455 88, 98
OW     '68-'72   442, W-30 and H/O
OW     '70       4V 455 w/W-30 442 (4400 series)
OW     '74-'75   4V 455 Cutlass (Calif)
OX     '74       4V 455 Cutlass (L-76)

Switch Pitch ID
To identify a TH-400 switch pitch transmission, look at the stator shaft. It has splines which are about half the usual length, and there is a large relief of the diameter of that shaft just behind the splines.


Used from '66-'78.

Pan Shape


Olds TH-425 ID's:
ID     Year(s)  Application
OJ     '66-'78   Toronado
OJ     '70       4V 455 Toronado, except W-34 (9400 series)
OJ     '73-'75   4V 455 Toronado
OM     '74-'75   4V 455 Toronado (Calif)

Switch Pitch ID
To identify a switch pitch transmission, look at the stator shaft. It has splines which are about half the usual length, and there is a large relief of the diameter of that shaft just behind the splines.


The TH-475 has been listed for HD trucks and some large old Cadillacs, but I have no info on it.

[ Thanks to Thomas Martin for this information. ]


The tail shaft is not removable - it is part of the trans housing casting.

Pan Shape
The TH-200-4R has an unusually shaped pan that almost looks like 2 parts. But the pan looks very different than the TH-350. It has a main pan and what looks like a small secondary pan at the rear. All TH-2004Rs have the word "M E T R I C" stamped on the bottom.


TH-200-R4 ID's:
ID     Year(s)  Application
KZF **              Olds 442/Hurst
CZF **              Monte SS
BRF **              GN/T-Type/Turbo Regals
OZ **               Hurst Olds
OM                  Olds 350 Diesels
OG                  Olds 307
BY                  V-6 252 Cars
AA and AP           Cadillac's
Transmissions marked "**" have a special (better for performance) valve body, plate, 1-2 servo, 3-4 servo, 2-3 intermediate servo, and governor.

These codes can be found on the passenger side of the transmission near the output shaft. Sometimes they are hard to read due to the catalytic convertor getting in the way.

The valve body itself will have the first two letters painted on it. Be careful because the paint comes off easily. The special valve bodies usually have a purple strip on them also.


Pan Shape
The TH-700-R4 pan is completely square.


[ Thanks to Scott, Chris Witt, Tom Millard, Tom Lentz for this information ]
[ Thanks to Steve Ochs, Bob Hale, Cliff Feiler, Mike Krumwiede, Stephen Hoover for this information ]

Automatic Transmission Comparision

GM built hundreds of variations of the same trans for differing applications. This is why it is important to obtain an identical or more heavily built unit, if you will be reusing stock components.

For example, 4-4-2 TH-400's differed internally from the full size models in several areas. The 4-4-2's valve bodies were calibrated differently to provide higher WOT shift points as well as a firmer shift. The direct clutch assembly contained different amounts of steel clutch plates and composition discs depending on application. The OW trans used in the W-30 used a different plate/disc setup all together. Torque converters differed between models as well. With different stall speeds to allow an acceptable idle in gear with the bumpier cams used in the 4-4-2's vs the full size models milder cams.

Two speed automatics were very common from the start in the early 1950s through the early 1970s. GM, Ford, and Chrysler all had their variants. At the time of the early Hydramatic when other companies were trying to catch up, it was thought that a two speed automatic with torque converter was a superior design compared to the four speed with fluid coupling design of the Hydramatic. A torque converter does torque multiplication just like a gearset does. A fluid coupling is strictly a pass-thru device. Eventually everyone caught on that two speeds were not enough, some quicker than others. Chrysler replaced the two speed Powerflite from 1953/54? with the three speed Torqueflite from 1956. Others took longer. At the bitter end, two speed automatics were seen only at the low end of the market (early Vega, amongst others).

Here are some comparisons of ratings:

                           Engine  Gearbox  Gross    Torque      Overall
Transmission       Weight  Torque  Torque  Veh. Wt. Conv. Dia.   Length
   Model           (lbs.)  (lb/ft) (lb/ft)  (lbs)    (inches)    (inches)
Rear Wheel Drive:
TH-180C (3L30)     130/140   258     440     7716   9.6/10.24   26.29/28.11
TH-200-4R          157       330     550     6000     11.73     28.26
TH-300 (Jetaway)
TH-400 (3L80)      190       440     885    12000     12.20     29.30/34.48
TH-700-R4 (4L60)   167/184   350     650     8600   9.6/11.73   29.77/30.64
4L30-E             168/177   258     440     7716   9.6/10.24   28.54/31.57
4L60-E             160/176   350     612     8600   9.6/11.73   29.77/30.64
4L80-E             260       440     885    15000     12.20     31.93/33.02

Front Wheel Drive:
TH-125C (3T40)     161       200     416     5100     9.64
TH-440-T4 (4T60)   195       235     369     5181     9.64
4T60-E             203       280     390     6400     9.64
4T65-E             214       285     400     6400   9.64/10.16
4T80-E             295       305     461     6800     10.43

Here are some common tranmission gear ratios:

   Model           First   Second   Third   Fourth   Reverse
Rear Wheel Drive:
TH-180C (3L30)     2.400   1.479    1.000     ---     2.000
TH-200-4R          2.741   1.568    1.000    0.674    2.067
TH-300 (Jetaway)
TH-350             2.52    1.52     1.00      ---
TH-400 (3L80)      2.482   1.482    1.000     ---     2.077
TH-700-R4 (4L60)   3.059   1.625    1.000    0.696    2.294
4L30-E             2.400   1.479    1.000    0.723    2.000
4L30-E Optional    2.860   1.620    1.000    0.723    2.000
4L60-E             3.059   1.625    1.000    0.696    2.294
4L80-E             2.482   1.482    1.000    0.750    2.077

Front Wheel Drive:
TH-125C (3T40)     2.840   1.600    1.000     ---     2.067
TH-440-T4 (4T60)   2.921   1.568    1.000    0.705    2.385
4T60-E             2.921   1.568    1.000    0.705    2.385
4T65-E             2.921   1.568    1.000    0.705    2.385
4T80-E             2.960   1.626    1.000    0.681    2.130

The difference between the transmissions is most likely the number of internal clutch plates. The main differences between models of the TH-4L60-E are: 1) different case, bellhousing, and extension configurations, 2) varying amounts of friction plates vs. steel plates in various clutch packs, 3) two different torque converter diameters.

Here are some power loss estimates:

If memory serves me the TH-400 takes approximately 45 HP, the TH-350 uses about 30HP, and the PowerGlide/JetAway uses about 20HP. I don't remember where I saw these numbers posted but they seem to fall pretty close to true. We used my friends '68 Chevelle as a test bed for the difference between the TH-400 vs TH-350. He picked up nearly two tenths by switching to the TH-350 behind his 327. He attributed this to 3 things:

1) the 350 weighed less.
2) the 350 has a slightly lower first gear (2.52 vs 2.48).
3) and finally the supposed HP loss difference.

The differences in loss also seem plausible when considering the size (mass) of the internals on each of these transmissions.

[ Thanks to Steve Ochs, Paul Elosge, Todd Daenzer, Greg Rollin for this information ]

Early Hydramatics

The four speed Hydramatic was considerably different from more modern automatics. It had NO torque converter! It had two fluid couplings (from mid-1950s on), one of which was used for shifting purposes. It filled and drained to effect one of the shifts, along with regular plate clutches for other shifts. The shift involving the fluid coupling was very soft and slow.

There were a lot of very interesting automatics in the 1950s, the Triple Turbine Dynaflow probably being the most unusual. It did no "shifting" whatsoever for normal driving, at least not in the normal sense. It had a multiple element torque converter (triple turbine), where each turbine was connected through a separate concentric shaft to a different gearset. During driving, as speeds and loads changed, the fluid flow through the torque converter would hit the different turbines in different proportions. So you never really shifted... you might have 60% of the torque delivered through third and 40% through second, with the proportion through third increasing as speed increased. Obviously this was a very smooth transmission, but the car was slow and the fuel economy was poor compared to more normal automatics.

For the 1950's, Cadillac and Oldsmobile used the Hydramatic (4 speeds). Buick used the Dynaflow (3 speeds). Chevrolet used the Powerglide (2-speeds). I am not sure what Pontiac used, but it was one of the above (I think the Hydramatic). Chevrolet also used a Buick Dynaflow at one point for their higher performance engine (for the 348 only (precursor of the 409)).

The Hydramatic used fluid coupling(s), while everything else used torque converters.

There were several variants of the Hydramatic and Dynaflow over the years. The early Hydramatic didn't have the second fluid coupling. The early Dynaflow didn't have three turbines, and I believe did actually shift through clutches for at least one of the shifts.

The Triple Turbine Dynaflow is nothing like the recent CVATs. Those CVATs are based on two variable diameter pulleys with a belt between them. The technology was originally developed by a Dutch auto manufacturer by the name of DAF (since acquired by Volvo). The 1960s version had a rubber belt in tension between the pulleys. This kind of worked for the car had something like 25 HP. The recent CVTs use a steel belt in compression. This works pretty well with a higher power engine, like 100+ HP.

The Dynaflow was a good automatic for the time, no one cared to much about fuel economy back then. It wouldn't be good today. There also was a performance penalty, but you could get around that with a bigger engine. Only problem was Buicks competitors kept using bigger engines too. There was a great horsepower race going on at the time.

The current steel belt CVT is supposed to be both good for performance and fuel economy. The driving characteristics are supposed to be a bit weird, at least compared to normal cars. The engine is somewhat constant speed, where when you initially accelerate, the rpms go up and then stay there pegged as the CVT slowly varies the ratio.

The original dual range Hydra-matic was a really strong trans for its day. It'll definitely stand up to a J-2 engine, but I'd recommend having someone familiar with it to go through it before using that combination. This transmission uses all friction clutches and bands with no sprag clutches. The second to third shift requires a simultaneous engagement/disengagement of all the forward clutches and bands, so timing and adjustment is critical to long life. Find someone familiar with this trans in your area to make sure that the friction material is in good shape and that the bands and linkage are properly adjusted and it'll give good life.

All of the first Hydra-Matics were 4 speeds from 1939 through the middle '50s. Dual range meant that you had several drive ranges on the shift quadrant & could lock in certain shifting patterns such as 2nd gear start for snow & ice or locking the car in 3rd for decending hills.

In terms of shift point labeling, 'S' did stand for Super, and this terminology was used at least since 1952. My 1952 Oldsmobile sales brochure has a discussion of Drive and Super, like it was a new feature for 1952. Back then it was the four speed Hydramatic, which went up to 1963-64 or so. This was replaced by the Turbo-Hydramatic, a three speed with torque converter.

Note that "Super" and "Second" may have different connotations. I seem to remember "Super" may have limited the transmission to first and second, with a different shift point between them than if left in "Drive". There were other automatics (Ford?) where the selections were "D-2-1", and 2 did mean second much more literally. Another set of selections were "D-L2-L1", which might have meant the same as "D-S-L". The current Chrysler Auto-Stick is another transmission where the gears are much more directly controlled while in that mode... 1-2-3-4 I believe can be selected more or less directly, as long as speed and rpm are not completely out of range.

Oldsmobile started using the "S" range in '52. They changed the name of the tranny that year to Hydra-Matic Super Drive. Hence the "S" stands for "Super Range." The quadrant read N-Dr-S-Lo-R. Note that Park was actually reverse with the engine shut off. Shutting the engine off threw out the parking pawl. Surprisingly, the '52 sales book doesn't tell you what "S" does, just that it was to be used "when you want super performance." The owner's manual doesn't tell you much either. I gave my shop manual to the guy who bought my '52 Ninety Eight, but I think it said in there that S kept the transmission in third up to something like 55 or 60 mph, then allowed it to shift into fourth. Lo was actually first and second, not just first. Dr, naturally allowed the trans to shift through all 4 ranges. From a standing start, these cars can go about 3 feet and they shift to second. Then there's a long pause until the shift to third. Then just that quick they go into fourth. Super was evidently used to prevent the premature fourth gear upshift when climbing hills and on powerful starts.


Electrical Connections



Overdrive & TCC Lockup Activation

1956 and later Hydramatic transmissions are different than the earlier ones. They have dual fluid couplings. 1955 and earlier Hydramatics have only one, which means that from a performance perspective you can get firmer shifts out of the 1955 and earlier transmissions than the later ones. This happens because the secondary fluid coupling on 1956 and later transmissions is an integral part of the transmisssion, and can't be removed for the transmission to work.

According to my shop manual, from sometime before 1954 and until 1955, you got what they call a "Dual Range Hydramatic". In 1956, the Dual Coupling Four Speed Hydramatic was introduced, and was available until 1960. During this time it was produced in two different versions - one made from 1956 to 1959, the second had a run from 1959 through 1960, although the differences look minimal. In 1961, the book lists a "Three Speed Hydramatic" being introduced, with a scaled down version used in the early F-85. I'm pretty sure it's unrelated to the TH-350, and I think it was used until 1963 or 1964, whenever the slim jim was introduced.

TV Cable Adjustment

[ Thanks to Paul Elosge, Bill Culp, Ernie Johnson for this information ]


The Powerglide transmission has less parasitic loss.

It should NOT be used in a vehicle weighing more than about 3000 lbs. It's not strong enough, even with heavy duty (read expen$ive) parts.

Electrical Connections



Overdrive & TCC Lockup Activation


TV Cable Adjustment

[ Thanks to Steve Ochs, Jack Wendel, Jim Chermack, others for this information ]

Jetaway / TH-300

I have a sneaky suspicion that that old Jetaway will always be a leaker. I replaced the pan gasket, the filler tube seal, and the tailshaft gasket, and checked all of the servo points for leaks - it still leaked. The front seal to the torque converter wasn't leaking either. Just a shady guess here, but does yours leak from the front passenger side corner?


Electrical Connections
The electrical connection on the Jetaway is for the downshift solenoid.

The 2-speed automatics from 67 to 69 found in Cutlasses downshift electrically. The kickdown switch is mounted on the firewall. It's mechanically connected to the throttle linkage, and has a couple of wires going down to the side of the tranny. Kickdown is activated by a switch mounted at the accelerator pedal under the dash.


Overdrive & TCC Lockup Activation

Some (maybe most?) were switch pitch. Those that were not tend to be teamed with lower performance engines and tend to be base model vehicles.

TV Cable Adjustment

[ Thanks to Greg Beaulieu for this information. ]


The TH-350 will handle in exccess of 550 lb ft of torque if built right. I have used one behind a brutal 455 for 5 years with NO failure of any part. It would spin the tires for 30 feet going into second and chirp them hard going into third. Keep the fluid changes to 12,000 miles, and put an auxilary cooler on it. As a note it takes 14-18 less horsepower to turn the TH-350 compared to a TH-400. So you are freeing up some horsepower. It also has a slightly lower first gear.

The 350 was the transmission of choice for drag racing up to about the late '70s as it was easy to build up strong. The TH-350 was the tranny of choice for drag racing because it has less internal mass and weighs less initially. But, for the same reasons, it is not as strong. The TH-400 and TH-350 use the same converter.

[ Notice: ]Please refer to the TH-350 section as well!

The weakest point of the TH-350 is the sprag and the output shaft. If you really want to put some power to it you must replace these. Install a good shift kit to keep the slippage and heat out of the tranny.

Electrical Connections
The TH-350 has no electrical connections. The only 'wire' connection on a TH-350 is for the back-up lights. The TH-350 uses a downshift/T.V. cable.

During full throttle conditions a kickdown cable provides downshifts for passing as well as higher rpm shift points for max acceleration. The TH-350 kickdown cable accomplishes this, with everything being mechanically actuated through the cable.

Generally these cables mount right below the throttle cable on the carb and are pulled. This cable is only for down shifting, AKA passing gear. You can run the car without it, the transmission will just shift earlier than usual under heavy throttle. Also if you pull out to pass, the car will not downshift when you hit the gas, you will have to downshift manually. I run mine disconnected in my m*libu street/strip car because I need to short shift the tranny manually for consistency. It is a little bit of a pain on the street when passing, but I can live with it and it's not worth the trouble to reconnect it each time.

There were at least 2 different configurations for this. The '69-'72 A-bodies had it attached to the throttle pedal assembly and it came thru the firewall. The '77-'79 full sizers used the setup where it attached to the throttle arm of the carb and requires a bracket that mounts between the carb and intake.

All the TH-350s I've seen have the downshift cable set up to be pulled at WOT. They typically pass through the firewall in the general vicinity of the throttle cable and attach to the gas pedal. All the 69-72 A-body cars use this arrangement. Unfortunately, I'm not that familiar with the 73-up cars.

I also have a dim recollection of seeing a car (the year and type escapes me, unfortunately) with the downshift cable attached to the carb. In this case, the carb's throttle lever extended below the throttle shaft to allow the downshift cable to be connected in a "pull" configuration.

The easy way to determine if your car had the cable attached to the gas pedal is to look at the firewall near the throttle cable. If there is another square punched out hole, your downshift cable should connect to the gas pedal.


Overdrive & TCC Lockup Activation

There is a difference between the 6 cylinder version and the 8 cylinder version of the TH-350. The 8 cylinder version uses more clutch plates for greater clutch capacity whereas the 6 cylinder version uses a thicker clutch piston to make up for the smaller number of clutch plates. Also, GM built special versions for the Corvette and police cars; heaviest built of any of the TH-350.

VERIFY THIS - PROBABLY WRONG (375): The TH-350B is a heavy duty version of the TH-350. Also a long tailshaft 350.

The TH-350C is a lockup version of the TH-350, and the electrical connection on the TH-350C is for the TCC clutch, not the backup lights. Backup light switch is either on the column or shifter assembly.

TV Cable Adjustment

[ Thanks to Steve Ochs, Jack Wendel, Jim Chermack, John Pajak, Joe Padavano, Dave Wyatt, Greg Beaulieu for this information ]


There are two TH-375s: the TH-375 or TH-375A, and the TH-375B. The TH-375A is the more common, medium duty version of the TH-400. The TH-375B is a less common, heavy duty version of the TH-350. Used in certain full size Buicks in the mid 70's.

[ Notice: ]Please refer to the TH-350 section as well!

A longshaft TH-375A is like a longshaft TH-400, but it uses the smaller diameter yoke from the TH-350. Pan shape is that of the TH-400. The only difference is the output shaft and the tailshaft housing. The TH-375A has the guts of a TH-400 with the output shaft of a TH-350. It was used in full size cars, and it effectively shortened the drive shaft. The TH-375A is also often swapped into big cars as a direct replacement for dead longshaft TH-350s.

Electrical Connections

Same as TH-400 (TH-375A), or TH-350 (TH-375B).


Overdrive & TCC Lockup Activation


TV Cable Adjustment

[ Thanks to John Pajak, Stephen Hoover for this information ]


The TH-400 transmission debuted in 1964 Cadillacs. All GM full size vehicles used TH-400's from 1965 and onward. The book How to work with and Modify the Turbo Hydramatic 400 Transmission (recommended) gives a complete list of GM division usage codes. The breakdown is as follows:

B: Buick
A: Cadillac
C: Chevrolet
O: Oldsmobile
P: Pontiac
C, F: Chevrolet/GMC truck use C until 1980, then use mostly F until 1988

More exotic brands that came with Turbo 400s (knowing it was the best in the business and/or couldn't manage to make a decent transmission themselves):

MA: 1984-88 AM General 4WD Military Truck
FV: 1981-82 Avanti with 350 V-8; Excalibur (?)
N: 1973-82 Checker
FE, FG: 1977-80 Ferrari (V-12)
E: 1971-78 Holden (never heard of this ... anyone?)
Z: 1976-88 Jaguar
K and J: 1965-79 Jeep
EA: 1969-76 Opel Diplomat
RV: Revcon Motor Home
R: 1966-88 Rolls Royce
ET, EV: 1977-88 Volvo Truck

[ Notice: ]Please refer to the TH-400 section as well!

One of the best, if not the best, transmissions ever made.

Electrical Connections
Two different kickdown switches have been used. A 1 prong and the 2 prong switch.

The second prong on that connector is for the high-gear vacuum switch that directs vacuum to your distributor advance unit in high-gear only (an emissions item that doesn't affect performance). It only allows the solenoid to open in high-gear; I don't know if it is normally closed and only opens when a switch in the transmission (which, I suspect, is absent from the transmission he installed in there; it's specific to the early '70's trannys, and part of the valve body, so it's more than just the proper connector).

The second terminal you mentioned, is for the electric solenoid on top of the thermostatic vacuum control valve on the front of the intake manifold. There was a big ol electric switch up there, that, when a pressure switch inside the tranny saw pressure for third gear, it would ground the solenoid, and pull the valve up to port vacuum to the distributor. That is the reason for the "second" terminal. Not all trannys had this, and it's no big deal if yours don't, unless you are restoring to factory original status. If you routed your distributor vacuum to a ported source, you don't have any use for that switch.

To check the kickdown solenoid, you can do one of two things, you can either hook up a 12 volt source to it and listen for the "click" or you can turn the ignition to the "ON" position, and have someone floor it to activate passing gear. You should hear the click. Also, make DANG sure you know which wire goes where. It may be a case of just swapping the wiring in the terminal boot.

The electrical connection on the TH-400 is for the downshift solenoid. Unlike other GM transmissions, the TH-400 does not use a downshift/T.V. cable. The kickdown switch is mounted at the accelerator pedal under the dash. It sends 12 volts to a connector on the side of a TH-400 case during full throttle conditions. This then energizes a solenoid inside the trans providing downshifts for passing as well as higher rpm shift points for max acceleration.

Filter Differences
The early (1965-67) TH-400s used a different filter than the 1968 and later models. Actually a much better one. They are hard to find too, but should be out there somewhere if you look hard enough. It has a long metal body with an internal filter element and metal pickup assembly.

The later filter can be used but requires changing the pan to the later version as well. If the early filter can't be found, I think any later model pan/filter combo will work.

The valve body will also need to be drilled and tapped for the screw that holds the later pancake type filter. It's not hard. But as I said, the early filter is supposed to be better. That opinion comes from trans techs of the era who said the pancake filter was/is cheaper to manufacturer, box, store, etc. The early shape is roughly "U" with the pipe, long metal filter element and pickup. Big box, takes up a lot of shelf space.

Actually, there were 3 lengths of TH-400 tail shafts.

Manufacturing Changes
Be cautious. The 1969 casings are identical, but the guts aren't necessarily so. The center support in early 1969 casings did not have the 0.040" spacer ring in there to protect the casing from the slamming of the center suport. Later 69's, (after around March) and newer TH-400s had the spacer, and therefore a 0.040" thinner center support. That spacer is a case saver. So you may want to ensure the internal lugs where the center support go aren't beat to heck.

Overdrive & TCC Lockup Activation

TH-425 (FWD), TH-475. Under new GM lingo, it was also known as the 3L80.

TV Cable Adjustment
No TV cable used.

[ Thanks to Graham Stewart, John Pajak, Mike Rothe, Greg Beaulieu, Bob Barry, Bob Handren, Jim Chermack for this information ]

TH-350 vs. TH-400

Consider this- why did the factory put TH-400s behind the big-inch engines, while the TH-350 was put behind the small-inch engines? Because the TH-400 can handle the increased torque. The TH-350 has a lighter internal rotating mass, but must be modified to handle increased torque loads. With this done, it will make a good performance trans. I particularly like the TH-400 because you can beat it to death and it is ready for more. The only transmission I've ever killed was a TH-350. I put it behind a modified 455 and thought I might get away with it. It was fine until I put a good hooking set of slicks on the car. I've yet to destroy a TH-400.

If you have a 2000 stall torque convertor for a TH-350, you "automatic"-ally have one for the TH-400. They will interchange with each other. But, depending on the torque input, that stall speed is raised or lowered from that "general" 2000 stall reference point. If you are going with a modified engine, and a lot of horsepower and torque, you will have to modify the TH-350 to equal the load capacity of a stock TH-400.

Well, then, I'll say it now: the TH-400 is a better tranny. But, better for me means more reliable for everyday use on the street. Better for somebody else might mean it's 3/10ths of a second quicker through the quarter-mile when sufficiently modified, in which case they'd consider the TH-350 better.

For me, I'd gladly sacrifice 3/10ths at the track for 200,000 miles of trouble-free service. My latest TH-400 only needed a rebuild after 18 years and 220,000 miles; I've had them go at 90,000 miles, but that's when the previous owner had ran it low, and it took five quarts to even get to the bottom of the dipstick. Even then, I was able to drive it to the tranny shop, though just barely. My latest TH-350 was getting "reluctant" to go into reverse (it wouldn't go in at all until warm), after only 90,000 miles, though it may have been due to abuse from a previous owner.

Build your TH-350's for the track, and I'll take my stock TH-400 on the street.

Both transmissions are world-class trannys (which is why Rolls-Royce and Jaguar used the TH-400 in their cars; they couldn't build a better one). Either will suit any application, though the TH-400 is a better starting point for longevity, since it's inherently stronger (bigger parts), whereas the TH-350 is a better choice for quickness, since its rotating parts are inherently lighter (smaller parts). Short of class racing, though, I wouldn't bother to switch one for the other.

[ Thanks to Mike Rothe, Bob Barry for this information. ]


Well, it's my understanding that the TH-425 was basically a TH-400 severed aft of the torque converter. A chain drive was mounted to the truncated transmission and the remainder of the transmission and differential mounted below for FWD applications. There's a good picture of one at

[ Notice: ]Please refer to the TH-400 section as well!

Because it is basically a TH-400, it is one of the best transmissions ever made. It was over-engineered for introduction in the Toronado.

Electrical Connections



Overdrive & TCC Lockup Activation


TV Cable Adjustment
No TV cable used.

[ Thanks to Patrick Flowers for this information ]



Electrical Connections



Overdrive & TCC Lockup Activation


TV Cable Adjustment

[ Thanks to for this information. ]


The TH-325 shares some parts with the TH-200 [clutches,drums etc]. I assume the TH-325-4L [od] shares parts with the TH-200R4.


Electrical Connections



Overdrive & TCC Lockup Activation

The TH-325-4L, a longitude (RWD) 4 speed version of the TH-325.

TV Cable Adjustment

[ Thanks to Kevin Wong, David Brode for this information ]


A light three speed transmission that is the same length as a TH-350. Remember, the TH-200 and TH-200C have no vacuum line (hence no vacuum modulator), only a TV cable, check and readjust. It's adjustment can destroy a tranny if incorrectly adjusted. The modulator is controlled by the TV Cable. It is not a downshift cable like the TH-350's.

If the original trans is a TH-200 then it is probably not worth rebuilding. A TH-200 is not a performance transmission from a conventional standpoint. The first thing to do, if it shifts poorly, is to service it. A used TH-350 will cost less than a rebuild for a TH-200, and will last longer. The proper way to rebuild a TH-200 is to replace it with a TH-350, which would be both cheaper and stronger.

Electrical Connections

Through the TV cable.

Same as the TH-350.

Overdrive & TCC Lockup Activation
No overdrive. The "C" model employs torque converter lockup under certain conditions.


TV Cable Adjustment
Correct adjustment is usually to press in on the rectangular button on the cable, press it towards the back of the car. Then move the carb throttle lever to WOT (DO NOT USE THE GAS PEDAL!!), let go of the TV cable, then the throttle, and it will self adjust. Just make sure you WOT the throttle lever on the carb! Check your service manual if you have any questions on this.

[ Thanks to Thomas Martin, Bob Barry for this information. ]


[ Notice: ]Please refer to the TH-200-4R section as well!

What probably kills the original TH-200-4R tranny is shift quality. The stock pump and pump pressure is too low for hard shifts. Note: the 1986 and prior TH-200-4Rs shifted fairly hard in stock form. The 1987 units were recalibrated and have a soft 1-2 shift at WOT. Also, the stator support is not strong enough for hard shifts.

The big killer is not the 1-2 shift, but the 2-3 shift. A real hard 2-3 shift at full throttle will break some internals in the tranny. The goal is a firm, quick shift but not a rapid, hard neck breaking shift. I modified my TH-200-4R for a quicker 1-2 shift. It now shifts quick and firm (will chirp both rear tires) but it is not a harsh shift. Note that high performance rebuilt TH-200-4Rs have hardened stator supports and other features to eliminate this problem.

A lot of replacement transmissions get trashed by dirt and debris in the system. What most people miss when the transmission is rebuilt, or convertor replaced, is the transmission cooler in the radiator, or an auxiliary cooler. If those are not flushed THOROUGHLY, the debris from the previous transmission failure will destroy the next transmission in short order. The majority of the warranty repeat failures we see are caused by re-using a converter or improperly flushing the cooler. This is witnessed by a failure rate in dealer replaced transmission of 3 times the rate of factory installed tranmissions. The failure rate is the same for both factory new transmissions and factory rebuilt transmissions.

Yes a 200-4R can be built to withstand 450 lb/ft of torque, but if it is in a heavy vehicle - it won't take much abuse. The Grand National is a lighter vehicle. It really is a combination of torque and gross vehicle weight that affect the capacity of the transmission

Electrical Connections
A late model TH-200-4R has 3 wires: 2 are used for the TCC solenoid, and the other is to signal the computer when 4th gear is engaged. The transmission will function without the wires connected. However, running the TCC disengaged on a TCC equipped transmission will lead to more transmission heat buildup, hence reduced economy and longevity. This is probably more of a concern on an overdrive tranny like the TH-200-4R, where there is actually a built-in overtemp switch which closes when the fluid reaches 260F, and forces the torque converter to lock-up during 4th gear operation. The lockup feature requires at most 2 wires. If the 3rd is for reverse light operation, you'd have to find an appropriate gear selector switch for the steering column to wire this in, if going from a 3-wire to a 2-wire hookup.

Electrical Connections



Overdrive & TCC Lockup Activation
The overdrive in a 200-4R is activated by the valve body in the trans if it is an 1988 or older. The torque converter lockup is activated by computer. You could either ignore it and suffer in gas mileage or activate the lockup via a switched 12 volt source. There is also a kit availible that will lockup the converter automatically using some type of pressure sensor in the valvebody. If the car was originally availible with the overdrive then the means for automatic lockup by the car's computer may already be there. Ignoring the lockup may cause exessive heat buildup due to the torque converter slippage and lead to premature transmission failure.

The ECU is normally used to lock up the convertor in 4th gear electronically. You can do a little re-wiring and replace the pressure switch in the transmission (from normally-closed to normally-opened) to make the converter lock up. Details are on the WWW page

A switch is installed internally in the 4th gear oil line. Only, and always, in 4th does it lock. One can wire a defeat switch on the dash, plus a vacuum-operated switch for unlock at WOT. The parts for this application are now common, and are even sold through Summit.


TV Cable Adjustment
Correct adjustment is usually to press in on the rectangular button on the cable, press it towards the back of the car. Then move the carb throttle lever to WOT (DO NOT USE THE GAS PEDAL!!), let go of the TV cable, then the throttle, and it will self adjust. Just make sure you WOT the throttle lever on the carb! Check your service manual if you have any questions on this.

[ Thanks to Bob Valentine, Kevin Wong, Greg Pruett, Thomas Martin, Steve Ochs for this information ]


A light duty 3 speed version of the TH-350 tranny. The TH-250 and TH-350 are almost identical, except the TH-250 uses an intermediate band for all 2nd gear applications where the TH-350 uses intermediate clutch for automatic 2nd gear and the intermediate band for manual 2nd gear.

I would recommend replacing a TH-250 with a TH-350, since the TH-350 is a bit more durable.

Electrical Connections


Overdrive & TCC Lockup Activation
No Overdrive. The V-8 models I've owned and driven of this vintage do lock the torque converter a little early for my liking. The V-6 models lock at 40 MPH. The easiest fix is to disable the LTC, which involves either installing a switch into the LTC circuit, or totally disconnecting it altogether. The first choice will give you the option of switching in the LTC for highway driving if you want to.

Another thing which happens to this model with high miles is that the plastic end of the speedo cable twists off, leaving you with no speedometer reading. When that happens, and it will, you will see that the LTC no longer locks up at all. Reason for that is the speed sensor on the speedo no longer works and so the computer will no longer send the signal to lock up the torque converter.



TV Cable Adjustment

[ Thanks to G. Douglas Burton for this information ]


The 700-R4 (and now the 4L60 and 4L60-E) is basically a THM-350 with overdrive. Yes, some of the components (pump, valve body) are aluminum now, but many components are carryovers from the 350.

The 4L60 is also known as the TH-700-R4. A great bang for the buck trans. A 3:1 1st gear gives good acceleration. The performance disadvantage is the large spacing between gears. I also hear that under high torque situations overdrive is the first gear to go - clutches can't handle the stress. There are also different versions of the valve body, some don't allow overdrive to engage if you have full throttle. I believe only the Corvette valve body will allow OD and full throttle. But heck, $1200 for a B&M version of this trans is an absolute bargain, especially compared to others. You will need a new torque converter and they can be expensive - but you will still come in under what the 5-speed would cost you.

[ Notice: ]Please refer to the TH-700-4R section as well!

1985 and back versions are not known for reliability. Get an '86 and up trans. The TH-4L60-E (TH-700-R4) was improved again in 1996. Shift quality and durability was enhanced. But the real choice for heavy duty racing is the TH-4L80-E or the four speed TH-400.

Electrical Connections



Overdrive & TCC Lockup Activation


The TH-700-R4 is now known as the TH-4L60 and TH-4L60-E. The 4L60-E is just an electronic version of the 700-R4 (4L60) with some other updates such as a better pump, etc. The TH-4T60-E is a FWD tranny. The TH-4T65-E is new for 1996 for the Hi-Po applications (Grand Prix GTP, Riviera S/C, Monte Carlo Z-34, etc).

TV Cable Adjustment
Correct adjustment is usually to press in on the rectangular button on the cable, press it towards the back of the car. Then move the carb throttle lever to WOT (DO NOT USE THE GAS PEDAL!!), let go of the TV cable, then the throttle, and it will self adjust. Just make sure you WOT the throttle lever on the carb! Check your service manual if you have any questions on this.

[ Thanks to Steve Ochs, Thomas Martin for this information ]


If you want TH-400 strength with OD, how about trying to find a 4L80? These are basically a TH-400 with overdrive - there wasn't a mechanical 4L80 with overdrive. All 4L80's were electronically controlled, so I guess they were all 4L80E's. You could always hook up an electronic controller though. But you probably won't have much luck finding this tranny in a junkyard though, best bet is buy one new from GM or from a tranny vendor.

The 4L80-E is the overdrive replacement of the TH-400 (using many carryover components), but is expensive because you need a controller for it (it is electronic shift). A TH-4L80-E with controller is around $1800-2600 I believe. There are kits on the market with a stand-alone computer, and none are cheap.

The TH-4L80 has not been used in a passenger car for quite a few years. It was optional in some 3/4 ton trucks and vans and standard in many 1 ton & up trucks and vans. Passenger cars have been using TH-4L60 trannys. I believe the TH-4L80-E is still an integral bellhousing.


The 4L80-E is just as strong as a THM-400. I believe almost 60% of the parts are carryover from the THM-400. It is the perfect overdrive replacment for the THM-400. There are a couple of companies selling the 4L80-E and also selling a controller for it. The nice part of having hte controller is adjustable shift points and adjustable shift firmness.

Electrical Connections

The TH-4L80-E is an selectronically controlled trans. This means a computer of some sort must be used to control not only shift points, but shift harshness. If you are rolling your own computer you can really do some cool stuff. The trick is to use the diesel computer and have someone reprogram it. HotRod or CarCraft showed a Buick GN with an aftermarket computer controlling the trans. Pretty slick, simply by reprogramming the trans using a laptop compuer, the trans could go from race to street.



Overdrive & TCC Lockup Activation


TV Cable Adjustment

[ Thanks to Tom Lentz, Steve Ochs, Joe Padavano for this information ]

Overdrive Transmissions

The THM200 4R and THM700 R4 have real OD gears, they are planetary gears with a lockup converter, so in a sense you would feel 5 shifts!

The TH-200-4R has a composite Chevy/BOP case. Acutally first overdrive made by GM. Manufactured from 1981 through 1990 - when the last non-chevy RWD (Olds) engine was made. This was always the limiting factor that prevented the F-car from getting the 3800. When the repaceable bell housing came out, other applications other than Chevy could be used. The 1989 Pontiac Anniversary Trans Am with the 3.8L Buick Turbo from the Grand National. Of course this F-body had a Buick 3.8L in it BUT it used the TH-200-4R trannsmission which was unique for the F-car.

The TH-700-R4 was only built at the Toledo plant (which was a Chevy TH-350 plant) before Hydramatic took over in 1983 - which is when 700-R4 production started. BTW - the 1983 through 1985 TH-700-R4s are not the greatest for reliability - many major modifications took place for the 1986/1987 time frame.

My sources at Toledo say there were no BOP composite TH-700-R4 cases made, only Chevy/FWD composite cases. Another possibility is that the cases you have seen were from a Holden (Australia). They are heavy into RWD and have some interesting combinations.

The final possibility is that they were specials for racing or another application, and not publicly avaialable, which would explain the lack of general knowledge of these units. Special cases for non-production vehicles could exist, but yes, they would be expensive due to the rarity and the cost of die-casting tooling to make such an animal.

If you note, the engine torque rating for the TH-200-4R and the TH-700-R4 is very close in stock form. Considering the weight advantage, the gear ratio preference, deeper overdrive, and the fact that the TH-700-R4 only comes in Chevy bolt pattern, the TH-200-4R is preferable for most BOPC street applications when built properly.

[ Thanks to Thomas Martin, Steve Ochs for this information. ]

Switch Pitch (TH-400, TH-425 and Jetaway)

The TH-400 switch pitch torque converter DOES NOT provide overdrive. It does provide two different stall speeds in the torque converter, and this might be considered to be an "extra gear". The transmission itself is still a 3-speed with ratios of 2.48, 1.48, and 1.00 to 1.

The dual pitch converter has a normal stall speed of about 1800 RPM, and it multiplies torque just like any other converter when in the normal mode. In the high stall speed mode, the converter stalls at about 2800 RPM but it DOES NOT multiply torque. If you have a large displacement engine with a lot of low RPM torque, this works well. If you have a smaller engine, or an engine with a very long cam which doesn't start to make much torque below 3000 RPM then you will probably be disappointed with the dual pitch converter. In any event, the dual pitch converter will not provide overdrive.

[ Notice: ]Please refer to the Switch Pitch Detail section as well!

If you can get an eletrical power source to the tranny, put the key in the ignition in the run position, disconnect the throttle rod from the carb (to keep from flooding the engine), and simply move the throttle rod back and forth. If you listen carefully as you move it from idle to WOT, you'll hear the switch pitch, or at least the kickdown switch clicking. If you hear two clicks through the travel, you have functional switch pitch and kickdown. If only one, then you have one function, but not the other.

The order across the throttle travel is switch pitch first (usually, just off idle), then kickdown almost at WOT.

Same as the regular TH-400, TH-425 or Jetaway, depending on what you have.

Electrical Connections
Same as the regular TH-400, TH-425 or Jetaway, depending on what you have.

Same as the regular TH-400, TH-425 or Jetaway, depending on what you have.

Same as the regular TH-400, TH-425 or Jetaway, depending on what you have.

Overdrive & TCC Lockup Activation


TV Cable Adjustment

[ Thanks to Steve Ochs, Christian Fair, [email protected], Bob Hale for this informatiton ]

Automatic Transmission Swapping

In general when swapping automatic transmissions on a vehicle equipped with an Olds engine (or Buick, Pontiac or Cadillac engine), you can swap in any transmission or bellhousing with a B-O-P bolt pattern. That gives the choice of the TH-400, TH-375, TH-375B, TH-350, TH-350C, TH-200-4R, TH-250, TH-200 and, of course, the old Jetaway.

If your speedometer reads wrong, don't suffer. Pull the transmission speedo gear, trot down to the dealer, and buy a replacement gear for around 7$. A very easy operation. Simply lift the front of the car and find the cable going to the side of the tranny. The cable is removed easily and the gear slides into a metal housing that also is easily pried out of the tranny with a screwdriver. You need to calculate how far off your speedo is before you pull the gear.

For example, 9 - 13% too low (speedo reading too low). This particular gear has 22 teeth, so buying the 20 tooth gear makes the speedo more accurate, although I think it is still around 2 mph short at 70 MPH. Better than before. Anyway, the point is, if you have an inaccurate speedo, its a very easy fix and inexpensive too.

However, ensure the reason that your speedo is off because a different plastic gear is used for your specific combination of differential gears, tire diameter and transmision. Check the manufacturer info on things like recommended tire size, rear end ratio, drive gear in the transmission (pain in the butt if this is wrong), and driven gear specs. If you require a reduction gear, that info is on there too. Especially if you have numerically high gear ratios like 3.91, 4.33, etc. All these things matched together equal fairly accurate speedo readings.

[ Thanks to Bob Barry, Todd Morris, Mike Rothe for this information ]

[ Notice: ]Please refer to the Transmission Swapping Detail section!

Automatic Transmission Rebuilding

I was able to compress the clutch packs using two large (~6-8") C-clamps. The C-clamp method of compressing the clutch packs took a couple of extra hands (be sure to compress the C-clamps evenly) and there were a ton of small parts to keep track of.

[ Thanks to Joe Padavano for this information ]

Automatic Transmission Tuning / General Information / Fundamentals

Bad Torque Convertor

With one bad GM torque convertor, it made a painful sounding scraping noise any time the engine was running, regardless of what gear I was in or if the car was moving. Remember that the TC is always being spun by the engine. If yours has this symptom, it's simple to check. Just unbolt the TC and push it back, then start the engine. If the noise is gone look hard at the TC. If your TC has failed you are certainly looking at a trans rebuild, since all those fragments get pumped through the trans and into any cooler.

In another case, the first symptom was that the transmission fluid turned black, not from burning (it didn't smell bad), but from microscopic particles of metal in it. When I dipped the corner of a paper towel into the fluid, a dark area grew from the wet corner but soon a red area grew beyong the dark area. The particles were only able to travel in the paper towel when suspended by fluid, and as the fluid became more dispersed the particles stopped moving. The fluid continued to travel. (This technique is a poor man's gas chromatograph.) I continued to drive it for about 100 miles and it gradually began to slip.

I replaced the transmission and converter, and then pulled apart the old tranny. It was OK except for being 100% filthy everywhere. After many hours of cleaning I finally reassembled it and eventually put it back into service. I did replace the clutch plates which have a friction surface, figuring that they had particles embedded in them.

According to the post mortem performed by the vendor, it had died from too much torque and heat, which caused internal parts to interfere with each other, which caused them to wear, and finally to wear through so that there was no more mechanical connection. At no time did the converter make any noise or vibration.

I discovered that the torque converter can cause some vibration, if not set up properly. The Olds Chassis Manual suggested that a person rotate the torque converter 120 degrees (one set of bolt holes). Then test drive the car. If that doesn't work, it said to rotate it another 120 degrees. If that doesn't work, I would suggest looking at the tranny.

[ Thanks to Bob Hale, Katana72 for this information ]


Aftermarket coolers are designed to supplement, not necessarily replace, the in-radiator transmission cooler. In fact, installation guides include the use of the radiator cooler.

The external coolor should be in line before the radiator cooler. You can actually get the trans fluid too cold by putting the external cooler after the radiator cooler. The warm engine coolant in the radiator will ensure adequate warmth. The trans fluid must have a certain amount of warmth in order to do its job.

180° - 200° is what they consider the ideal temperature range for a Powerglide, and I wouldn't think TH-350 and TH-400's would be any different, possibly a bit lower would be better. Heat is definitely bad on transmission parts, so cooler is better, to an extent. You do want the fluid to be at an acceptable temperature, just like oil.

First, the oil flow: oil is picked up from the pan through a filter and a suction tube into the pump. The pump's output has a regulator attached to it, and this regulator controls the oil pressure to the main line by dumping the excess oil to a bypass port. The line oil goes on to do things such as apply clutches or bands, supply the modulator and governor valves, and precharge accumulators. The bypassed oil goes through the torque converter and the heat exchanger and then is routed back to the transmission where it is used for lubrication.

Second: what happens to the bypassed oil? This oil has some pressure and may have considerable volume. It exits the pump's bypass port and enters the torque converter through one of the hollow shafts in the front of the transmission. In the torque converter the oil picks up heat due to the converter's inefficiency. The oil flows out of the converter through another of the hollow shafts in the front of the transmission, and is delivered to a fitting on the side of the transmission. From there, a steel tube carries the fluid to a heat exchanger located in the radiator. After the fluid has been cooled or warmed by the radiator (more on this later), it returns through another steel tube to another fitting on the side of the transmission. The fluid is then routed to the internals of the transmission where it performs functions such as lubricating the bushings and bearings in the transmission, and supplying an oil film to the clutch packs and to the bands. The oil then flows back into the pan and restarts the same trip.

If you examine the location and orientation of the heat exchanger in the radiator, you will see that it is located where the radiator's bypass water flow runs. Normally, the heater core is fed from an engine tap before the coolant thermostat, so that it sees warm water as soon as any significant heat has been produced by the engine warming up. The return water from the heater core is dumped back into the radiator in a place where it will flow across the heat exchanger before it re-enters the water pump and makes another circuit. This means that the heater core water, which warms up more quickly than the main radiator water, also serves to warm up the transmission fluid in the heat exchanger. This is important because warm transmission fluid is only a so-so lubricant, and cold transmission fluid is even worse. You want to get the fuid warmed up as soon as possible in order to lengthen the life and improve the durability of the transmission. The waste water from the heater core flowing over the heat exchanger does this.

The heat exchanger also cools the transmission during normal operation. When the fluid is hotter than the radiator coolant then the fluid loses heat to the coolant, and the cooler fluid is returned to the transmission. The net effect is that the temperature of the fluid from the heat exchanger is loosely regulated to about 200 degrees Fahrenheit, and this warm fluid is used to bathe the working parts of the transmission.

There are several things that can be deduced from the above:

  1. You want the radiator heat exchanger to be the last thing in the hydraulic circuit before the fluid is returned to the transmission. If you add an external fluid cooler (a really good idea), place it before the heat exchanger so that the radiator heat exchanger has the "last word".

  2. Keep the restriction in any cooler low. Since a high volume of oil flows in this circuit at times, you need low restriction to avoid having pressure build up in the torque converter. That pressure buildup is bad for a lot of things, including the engine's thrust bearing, the torque converter, and the various bearings and washers in the transmission which handle the axial thrust load. In a really bad case, excess converter pressure can crack a transmission case.

  3. Do not block the hydraulic lines in any manner. This includes thermostats and shutoff valves. Blocking the fluid flow not only results in very high converter and line pressures, it also causes a lack of lubrication inside the transmission which will quickly lead to transmission failure.

  4. Keep the heater coolant flow through the radiator intact. If you wish to remove the heater, then use a piece of hose instead of the heater core, but let the coolant circulate around the heat exchanger in the radiator.

  5. Keep the inside of the cooling system in good shape. This maintains the effectiveness of the heat exchanger, and greatly reduces the likelihood of the heat exchanger corroding through. BTW, if engine coolant gets into the transmission then you will have to replace all of the friction materials in the transmission as they are made of paper and will disintegrate when wet.
[ Thanks to Blaine, Jim Chermack, Bob Handren, Bob Hale, Ken Snyder for this information ]


My tranny wanted to late shift under light throttle, and would shift harshly after I replaced the intake. In my case I was fortunate, I had forgotten to rehook up the tranny kickdown cable. Check the cable to make sure it's fastened correctly.

Take the governor out of the trans and make sure the valve body in the governor is moving fluently. What I would recommend is taking a shot of Brake Parts Cleaner to it and getting all the trans fluid cleaned off, then it should slide in and out easily.

Why this happens is that the clutches in the trans get torn up and occasionally, the residue particles catch in the govornor causing improper shifting.

[ Thanks to Dave Rogers, Gerald Hughes for this information. ]


The older transmissions used a governor to modulate shifts based on the car's speed, along with either a vacuum diaphram & electric kickdown switch (TH-400), or a "kickdown" cable (TH-350), which provided load or throttle opening information. Newer trannies also include computer-controls.

[ Thanks to Bob Barry for this information. ]

Driveshaft Balance

An out of balance driveshaft usually shows up as a vibration at all speed ranges.

[ Thanks to for this informatiton ]


I'll bet you launched the driveshaft because it was turning such a high RPM. Any rotating assembly has a point where it won't rotate any faster without going ka-boom. How fast a driveshaft can turn depends on the stregnth of the driveshaft and how well it's balanced. In addition if the driveshaft alignment is off the driveshaft won't be able to spin as fast as it could. I read an article about it in hot rod awhile back. (Don't remember exaclty what issue it was, I think it was within the last 2 years.) The article said it's becoming a bigger problem now that overdrives are abundant. Folks get an overdrive for their ride to keep the engine happy on the highway with low gears. Problem is, most driveshafts can only be safely spun up to something like 4500 rpm. (That's not the gospel, I don't have the article handy so I'm quoting from a really crappy memory. It could be more or less. )

One reason for the driveshaft coming apart (just a guess here) after you upshifted might be that you changed the driveshaft alignment ever so slightly when you let up. Perhaps if a U-joint, rearend bushing or tranny mount was slightly weak it would allow the driveshaft angle to shift when you let up. Something like that may not be a problem at lower speeds but at such high rpm it may have been the proverbial straw that broke the camel's back. Either way, the driveshaft just wasn't built to turn that fast.

You could maybe try a driveshaft out of a `87 442 or GN, they had some pretty low gears, maybe they had a stronger driveshaft or a more precise balance. You might also look into getting a stronger driveshaft out of a truck or a heavier car. They can be shortended and balanced, or of course you could have one custom-built. Obviously the cheapest thing to do is just keep it under 90, but what's the fun in that. ;) BTW, Was your driveshaft solid or one of thoes deals where there's an outer shaft that is bonded with rubber to an inner shaft? The 2-piece driveshafts are smoother but signifigantly weaker.

The good news is that it's very hard to break a driveshaft on a street car otherwise. Especially with an automatic and a light car. Most of the time a U-joint breaks before a driveshaft ever will.

Driveshafts with rubber dampers aren't any weaker than solid driveshafts. I am sure there are exceptions, such as old or poor rubber condition. A listee had a 1964 Cutlass that was converted to a 4-speed. That driveshaft was actually two pieces. One inside the other with a rubber damper. That car ran low 11's at close to 120mph, lifting the front wheels off the ground. That strong enough? The dampened tube should actually absorb some of the shock to boot.

The driveshaft for the Jetaway and the 4 spd are the same length (the 4 spd will be solid and the Jetaway will have a rubber insulated driveshaft). The TH-400 uses a shorter driveshaft and a different yoke than the TH-350.

Big/Small block are the same length, but the transmission is the difference (length wise). A shortening and re-balincing should be under $100 easily, and can be done by yourself reasonably easy if you want. A welder, grinder, and hammer's all you need (but duct-tape wouldn't hurt!)

To find out how much to shorten a driveshaft, check out the appropriate shop manual for your car. The various driveshaft lengths should be listed in there. If you do cut your own driveshaft, cut your original driveshaft on the yoke end, shorten it, and weld in the new yoke, if it works, enjoy, if not, you've wasted your time!

Since they are going to rebuild the tranny anyway, check the rear planetary assembly for extreme wearing and check end play before you tear it all apart. Sometimes, and I've seen this, the driveshaft is not cut to the proper length, most of the time it is too long. If this is the case, you will have no room for the driveshaft to slide back and forth as the rear suspension moves. The yoke then "bottoms" out on the tailshaft, trying to push the guts of the trans right through the torque converter. You know what happens next.

[ Thanks to Greg Pruett, Eric Aksomitis, Bob Handren, Mike Rothe, Jim Chermack for this information ]

Dual Gate Shifter

Dual gate is the Hurst term for an automatic trans shifter which has a pair of parallel tracks or "gates". The gate closest to the driver allows the stick to move in the normal P-R-N-D-S-L motion. The right side gate actually only covers the gears N-D-S-L. This right side gate, which is accessed by putting the stick in neutral and pushing it towards the right, contains a mechanism to allow rapid upshifting of the trans during racing while preventing the selection of the wrong gear. Starting with the stick in first (L) in the right side gate, you can push the stick as hard and as fast as you want (pressing slightly to the right while slamming forward) and the mechanism will stop the shifter in second (S). You can then repeat this process to go from second to third (D). In addition, since the right side gate stops at N, you cannot accidentally hit reverse (which could have disasterous consequences at the big end of the drag strip).

The term "his and hers" comes from the politically incorrect 60s, where the original Hurst aftermarket dual gate actually came with a lock and key to prevent the use of the right hand racing gate of the shifter. Presumably "he" kept the key to prevent "her" from racing the car when she took it. Hurst actually ran ads to this effect - one shudders to think of the reaction to such an ad today.

It is amusing to an old hot rodder like myself (and the owner of a dual gate-equipped H/O) to watch the reaction in the automotive press to the numerous "autostick" and "tiptronic" transmissions now on the market. Porsche was practically given credit for inventing the idea a couple of years ago, despite the fact that the dual gate was on the market in the early 60s. Even the 1970s vintage Jaguars had a similar type of shifter, though theirs was a J-gate, where you had to take the shifter all the way into first to get to the other gate. Coincidentally, the V-12 Jags also were TH-400-equipped.

Both Olds and Pontiac offered factory installed dual-gates in the late 60s-early 70s. The mechanisms are the same, but the sticks are different. The Olds stick has a bend in the middle, while the Poncho stick is straight. I'm not sure if the mounting brackets are the same, however. I have a couple of Poncho units at home; I'll try to compare them with the Olds unit tonight.

I also believe that the mechanism is the same in the aftermarket dual gate. Again, I'm not sure about the brackets, however.

Yep, you should be able to bang on the shifter as hard as you want and still only hit the next gear up. I assume you have the stick in the right side gate, and that as you upshift, you press the stick against the right side of the gate as you simultaneously push forward. Note that the stick is spring loaded to the left, so you do have to conciously press it to the right for this to work. If you still overshift, it is possible that one of the internal springs is broken, or the edges of the shifter gate have been worn and rounded, preventing a clean stop by the stick.

According to their web-page ( Mr Gasket is honoring the Dual Gate's lifetime warantee, and will rebuild a dual gate for $45.00 and about 2 - 3 weeks turnaround time. All the details are at their site. Cable Part Numbers
The GM part # for the dual gate cable is 406266. The non dual gate # is 407409.

[ Thanks to Cliff Simpson, Joe Padavano, Randy Geisel, Kevin Hoopingarner for this information ]

Final Drive Ratio

In general, what you want is the widest possible final drive ratio, so you can get good accleration at low speed and then wind the motor out to its torque peak in top gear. This is accomplished with expensive transmission parts.

On the manual side, you can use a modern manual 6 speed transmissions, getting great milage, and wonderful acceleration. This costs about $2500, plus time, and has been covered in Hot Rod Magazine, and other places. Expect to use a fairly steep rear end, like 3.73, 4.11 or even 4.56, so that the 0.50 top gear is usable.

On the automatic side, you can use a 4L60 or 4L80 OD transmission, either with or without supplemental OD. The best setup, a 4L80 with GVOD will be very very strong, should give you about 0.60 final drive, but it will cost $5000. A 4L60 can be had for a bit more than $1000.

[ Thanks to for this informatiton ]

Fluid Flush

It is also possible (and messy) to get virtually all the fluid replaced by disconnecting the trans cooler line to the radiator, directing its output to a bucket, and adding fluid to the tranny as it pumps out the line. You will need to stop now and then to replace the fluid that has been pumped out - don't go too low - about every two to three quarts. You will use around 12 quarts of new fluid.

Move the gear selector through the gears (foot on brake!) will the fluid is pumping out. The fluid will appear cleaner (and it's normal color and smell) as you get near 10 or 11 quarts. Pump a little more out, just make sure you have enough new fluid to top off the transmission.

It's not difficult, but it is messy and tedious. Two people working on this is much better than one. Of course, you still have to remove the pan to get at the filter. While the pan is off, perhaps you could install a pan with a drain plug to aid in this procedure (which should be done every 15,000 miles, or at least every other year if you don't drive that much).

[ Thanks to Dave Paulison for this information ]

Governor / Modulator

The governor and modulator work together. The modulator uses engine vacuum signal to vary the shift point, while the governor uses tailshaft rpm to help with shift points using vehicle speed. Both working in conjunction basically varies trans internal line pressures to allow the upshifts to occur at a certain speed depending on engine load condition. There is too much going on here to simplify it in a paragraph or two. The service manual is a good start to read up on how these little guys work.

The stock tranny does have a governor which limits RPM at which the trans should upshift. This is usually used to govern the RPM at wide open throttle.

If the vacuum modulator is not working properly, the trans will think the engine is at WOT and will upshift on governor command only. This will be a pretty harsh shift.

[ Thanks to Mike Rothe, Joe Padavano for this information. ]

Hard to Find Filters

If the Jetaway did not change filters between 1964 and 1967, the Fram FT1014 will fit. It is the replacement for the 1967 Jetaway.

[ Thanks to for this information. ]

Kickdown Cable Attachment

Among the automatic transmission that use kick down cables, here are some things to watch out for. First of all there are two different atachment clips at the carb. Make sure you have the one that matches.

Adjusting the length of the kickdown cable is very important, even more so on an overdrive transmission. If misadjusted, the trans will overheat and burn up. On a regular three speed, the trans will just act funny.

Adjust the T. V. cable until you feel the shift is at the proper time and RPM. Keep in mind, the '85 to '87 series are computer comtrolled transmissions. By adjusting this cable for a sooner downshift, you are also adjusting the shift points for all gears, and when your air conditioning will shut off at wide open throttle. So if you adjust the T. V. cable do it in small increments. Also, to help with the shifts I added an aftermarket ADS Powerchip in place for the factory PROM. I did not really notice much change in quicker pick-up but the shifts felt better and quicker. Basically the chip delays your torque converter lock-up in overdrive so you can rev longer before shifting.

On the kick down, look at the carb for the T.V. cable, that it the Throttle Valve cable, which replaces the downshift cable like the older THM 350's.

To adjust (the cable stretches over time, I do this every 6 months or so), press the button on the cable adjuster at the bracket in (can be hard to press), and push cable in from the away from the carb. Then (engine off please) move the throttle to full throttle. Failure to do this last step can damage the transmission!! DO NOT drive a THM 200 4R or THM 200C with the TV cable out of adjust, this can kill one of these transmissions. It will click till it self adjusts to the correct setting. That is all. Very easy proceedure.

A GM dealer trans guy told me of I wanted slightly better shifts to move it away from the carb (or Thottle body) one notch after it is set correctly, but if you are like me and stand on it (WOT) now and then, it will reset itself. The TH-200C, TH-200-4R, TH-700-R4, and the TH-440-T4 (86 up Delta 88 FWD) are all the same.

The routing of the cable is also important. Always try to route it in a manner similar to it's original installation. Avoid sharp curves unless they were intended.

[ Thanks to Dave Paulison, Cliff Feiler, Thomas Martin for this informatiton ]


If the flex plate to Torque Convertor bolts are loose, you will experience a vibration and a rather noisy clunking or knocking at any speed, in or out of gear. If the bell housing bolts are loose, then you will have a clunk and bump when you place the car in gear, and upon acceleration and deceleration.

[ Thanks to Kerry Kroger for this information. ]


That your trans leaks during times of protracted idleness is not surprising. The seal that goes around the torque converter frequently leaks in TH-400 series trannies in such conditions. When the trans is returned to service the seal softens and re-seals.

A common cause is the tailshaft seal leaking because of corrosion on the driveshaft yoke. If the car sat for a while the yoke can rust and when you drive the car the yoke moves in and out of the trans as you go over bumps. This will tear up the seal so that when you park it ATF drains out the back of the trans, especially if the car is parked uphill.

I've had the yoke seal on the tail housing (TH-400) leak when my car was parked pointed uphill. The seal had worn a grove in the yoke, so installing a new seal didn't solve the problem; a new yoke did solve the problem. The yoke will wear it down with age and can cause new seals to leak around the yoke in spite of the otherwise good appearance of the yoke surface. When this happens the leak is usually around the top half of the seal and is most noticeable when the car is parked up-hill. These bushings are in all tail shafts of all our Oldsmobiles, plus the lesser makes.

While replacing that O ring, jack the car up higher in the back. Run the engine for a minute to pump the fluid back into the converter, then shut it off. When the car sits for any length of time, the converter drains back into the pan, over filling it.

[ Thanks to Peter Berusch, Mike Bloomer, Robert Lavey, Dave Wyatt, Scott Woodworth for this information. ]

Linkage Adjustment

For having the reverse lights come on while the trans is engaged in reverse, you have a choice of two places to adjust: the steering column or trans linkage (underneath).

On the steering column you will find the starter interlock (neutral safety) switch, probably on the upper side of the steering column behind the dash. This is the gadget that prevents you from cranking the starter if you're not in Park or Neutral. It's also responsible for turning on the backup lights when you shift to the right spot. Its mounting holes are slotted so you can jiggle it a little to one side or the other to get it in synch with the shifter.

You have this on the column even if your car has a console shifter; the linkage in that case is "pushed" from the engine side rather than "pulled" from the column side, but the same switch hardware is in use. And I'm only talking about the '80's vintage here 'cause I just know somebody is going to nail me otherwise; if you don't find it there, I'm not talking about your car. So there.

The trans linkage is also adjustable for the same thing. I adjusted it down there when the aging motor mounts allowed the engine to sit lower in the cradle, which tended to pull the shift linkage out of synch and screwed up the backup lights. If you look underneath you should find one point where a setscrew bolt clamps onto a short bar, and loosening the setscrew allows you to slide the clamp back and forth a little on the bar. Fiddling with it a little bit (shouldn't need more than an inch or so of movement) there should get your backup lights back.

[ Thanks to Andrew Green for this information. ]

Lockup Torque Converters

The converter lockup is a fairly ingenious design. In a conventional torque converter, the fluid flows in one direction through the converter. This direction is the one that is most advantageous for flow. In the lockup design, the normal fluid flow direction pushes the lockup cone to its disengaged position. The lockup is achieved by reversing the fluid flow direction through the converter, and this pushes the cone into the housing and causes lockup. The flow reversal is done with hydraulics and is activated with a solenoid.

On CCC equipped cars, the computer ONLY controls the lockup torque converter. 4th gear (overdrive) is controlled by the valve body.

[ Thanks to Bob Hale, Kevin Wong for this information ]

Locking Torque Convertors

Locking Convertor
Once you attain a constant cruising speed the torque converter locks up to prevent any slippage and power/mileage loss. Standard on most new vehicles. A torque converter is BASICALLY 2 fans back to back and encased in trans fluid. One fan connected to the motor the other to the rear wheels through the transmission. When the motor fan spins fast enough it induces the second fan to spin and move the car. Obviously the second fan wont spin as fast, hence slippage. Once up to speed the 2 fans lock together to elimate the slip.

When swapping in an overdrive trans to a vehicle that did not have this feature stock, the rest of the vehicle really has to be setup for the overdrive trans. Namely the rear gears. For example, the final drive ratio of my Vista Cruiser with a 3.08 reaend and TH-200-4R overdrive is 2.06. That allows me to cruise at 1600RPM @65MPH and 1100RPM @45. The stall speed of the converter is only about 1500, and at such a low RPM I worry about bogging the engine too much, and there's not much pep with lockup engaged. I really need to change the rearend gears to take full advangage of the overdrive.

I quit using it because I figured the tranny was going to need rebuilt and beffed up inside of 12 months no matter what I did, it was a stock TH-200-4R behind an Olds 350. I just ignored it because I decided I'd rather have the extra pep, and I've been driving it that way for 2 years and 4 months now. The tranny fluid has never smelled burnt, didn't look bad when I last changed it, and (Knocking on wood) it runs just as smoothly as it ever did.

I still think the lockup is a good idea, but my car is just not set up right for it. When I get a decent set of rearend gears I hope to use it more. I also think that when you buy a TH-200-4R it's a good idea to get a lockup converter, and if you don't like it you can unplug it (or just leave it turned off).

I've never found out how big a difference it's supposed to make. For all I know it means the difference between getting 80,000 miles or 100,000 miles out of a transmission. But the more it gets abused, the less it's going to last, so it may make a bigger difference if you drive hard.

If lockup seems to come on too early, it might be a factory feature to keep emissions down.

[ Thanks to Greg Pruett for this information. ]

This is the arguement for how a lockup reduces heat. (hope it makes sense):

Using the lockup is mainly an issue with overdrive trannys, which allow for some seriously high final drive ratios. Even with say, a 3.55 rearend ratio, the final drive is still only about 2.38. With that ratio your cruise RPM will be in the neighborhood of 1900 RPM @65MPH and 1200RPM @45MPH depending on your tire size. The problem is that most stock torque converters stall at around 1400-1800 RPM, and high stall torque converters stall even higher. When the cruise RPM is lower than the stall speed of the torque converter, it slips more than it would if the stall speed were lower than cruise RPM. That's where the extra heat is generated.

In addition, if you have a high stall converter, you're going to generate even more heat than you would with a stock converter. That's why most people reccomend an auxilliary transmission cooler with a high stall converter. That's also why the conventional wisdom is to use a lockup if you have it. Most cars that came with non lockup converters have gear ratios of 2.56 or more. Most of the older Oldses have 2.73 or 3.08 ratios stock, which put cruise RPM higher than the stall speed of the stock converters, so heat generated by exessive slip was not much of a problem.

In stock form, GM BYPASSES the cooler partially when in lockup to make things WARMER to increase fuel economy. Many performance tranmssion builders eliminate this feature so that the cooler gets more fluid to it during lockup. I've read the lockup is worth 1-2 mpg, maybe more if you have a high-stall converter.

[ Thanks to Greg Pruett for this information. ]

Mechanical Lockup
For TC lockup, any lockup kit for the TH-2004R/TH-700R4 will work. The kit uses a vacuum actuated microswitch that engages the lockup under stable vacuum in 4th gear. This is the same method that GM used on non-computer controlled vehicles, such as my '86 Silverado work truck :)

[ Thanks to Stephen Hoover for this information. ]

TV Cable Adjustment
Does your 84' have Trans Valve (TV) cable? If you do, check the adjustment at the carb. You should have as much travel with the TV cable as you do with your throttle cable. If the TV cable is off, there is an adjuster near the trans to get it where it needs to be.

[ Thanks to Michael Hall for this information. ]


In terms of adjusting the modulator, you can only raise or lower the shift points 2 - 5 mph. Turning the screw clockwise will make it shift later and crisper. Turning counter-clockwise will make it shift earlier and softer. One full turn of the screw will change the modulator pressure by 2 - 3 psi. What it doesn't say is how many times you can or should turn the screw. I'd maybe try turning it clockwise one full turn and see what happens.

Overdrive - Aftermarket

Regarding the Gear Vendors (800-999-9555, 619-562-0060) overdrive unit, this unit is a overdrive/gear splitter unit with a 0.78:1 overdrive, and bolts directly to your transmission.. So this will take your 4.10:1 and turn it into a 3.20:1. The reason the overdrive is not steeper is because it is designed to also be a gear splitter, so you can go between gears (1st - 1st overdrive, 2nd - 2nd overdrive) for applications such as towing or racing.

For racing however, you would need a special computer control to take into account the approx. 1 second it takes to engage the overdrive. This unit is extremely well designed and constructed and comes complete with everything you need. The unit is operated by a two wire electrical connection, also a control box and an in line speedometer connection is included. The reason for the electronics is to prevent the unit from being engaged below 20 MPH, and to shut it off at approx. the same speed. Additionally, to provide for the automatic mode which automatically engages the unit at approx. 48 MPH.

This unit is rated at 2000 Horsepower (probably higher, but that's the highest they could test the unit). This unit is also expensive, it goes for somewhere around $2400.

I only had two problems with the installation: 1. The overdrive adapter would not clear the crossmember. I had the tubular type crossmember (typical on Chevy's) which did not allow the overdrive adapter to clear. I remedied this by obtaining a stamped type crossmember from a Pontiac Lemans (this style is typical on Olds Cutlass, Pontiac Lemans and Buick Skylarks).

2. There was insufficient floor clearance for the overdrive unit. If you pull the carpeting up on any 68-72 Chevelle, Skylark, Cutlass or Lemans, you will note that the transmission tunnel gradually necks down but then gets to a point where it quickly necks down further until you get to the front of the front seat sub-frame, where it gets larger again. This point where the tunnel is at its narrowest point (which is approx. 10-12" lengthwise in the car) is where you'll have clearance problems.

I tried to remedy this by using an air impact and a wide head hammering/shaping tool to enlarge to tunnel from under the car. At first, massaging the tunnel with this tool went smoothly, but right when I got to the point of having sufficient clearance, I poked through the floor. So, I ended up cutting this section of the floor away (approx. 12" by 12") and I shaped sheet metal to replace this piece. So now the tunnel on my car has a gradual neck down all the way to the front seat sub-frame.

But now I can take my car with its 4.10:1 rear end and cruise down the highway at a more reasonable RPM level.

[ Thanks to Sam Johnson, Erik Nowacki for this information. ]

Removing Servo Cover

From 2 Speed Transmission
If you're talking the low servo cover, it's held on with a snap ring. The 1968 Olds service manual makes it look like not much fun. Here's the blow-by-blow:

Removal of Low Servo Cover and Piston Assembly (on car):

  1. Remove transmission to support bar attaching bolts.
  2. Using wooden block, wedge block between transmission and floor pan (the photo makes this look like you actually wedge it between the passenger side of the trans and the trans tunnel).
  3. Using an awl through the hole in the case, press in on the cover retaining ring while prying inward on the cover. (The photo shows the awl going into the hole which is towards the rear of the car, a pry bar roughly paralled to the exhaust pipe pressing on the cover, and a screwdriver -see below - at 90 degrees to both of them)
  4. With the cover pried inward, remove the snap ring using a screwdriver. (This is where it would come in handy to have a 3rd hand)
  5. Remove low servo cover, inspect the cover seal, if nicked, torn or worn, discard.
  6. Remove low servo piston assembly from case.

To install, reverse the removal procedure using the pry bar to compress the cover while installing the snap ring. Torque transmission to support bolts to 52 ft. lbs.

[ Thanks to Greg Beaulieu for this information. ]

Shift Kit

When installing a shift kit, you may want to think about resealing the transmission. The reason behind this is that a shift kit increases the line pressure in the trans, and I have seen the internal seals just blow out after one good hard shift. The ability to chirp the tires is direct in relationship to the amount of torque the engine puts out. Make sure you change the fluid at regular intervals and it's a good idea to install a tranny oil cooler too.

They do increase the internal pressure, but I doubt it would cause the trans to leak (but anything is possible). As long as its in good working order you shouldn't have any problems, but if its slipping you might as well get it fixed you might even get the shop to install a shift kit for you.

A shift kit if anything will help you tranny last longer because it reduces the slipping and friction during shifts. The first kit I used was a B&M in a used TH-350 from a junk yard. Other than changing oil and spark plugs it was the first time I had ever done any work on a car. I put over 70k miles on that tranny before it went and the reason it quit working was because I got stuck in a snow drift and after about 20 minutes I found myself going from drive to reverse to drive at 3000 rpm. I got out but two days later I could only go 40 mph (and it took about 2 miles to get to that speed).

I've also used Transgo and I like their kit a lot better. Its easier to install, has more adjustability and cost about half what B&M kits go for. You shouldn't have any problems installing one in a day. You just got to be sure to keep everything clean and organized. The kit will have pictures to show you were everything goes if you forget. Read the instructions and get a good understanding of what you are doing before you do anything to the tranny.

Speedo Gears

The factory chassis manuals have a good section on this topic, listing differential gear ratio with certain transmissions.

Well, the answers at the Olds dealership about speedo gears was about as plentiful as finding sun + Palm trees here in the frigid stormy North East. They need year/model specific info to pull the GM info up. There reference Info only allows the scope of model options offered on that year including tire size. So there is no way to enter variables like a rear gear change higher than originally offered. Same with any tire size other than originally on the car.

What I did get after a little digging was a gear color/tooth reference chart. The only way to zero your speedo in is to pull the cable from the transmission and inspect the gear colors.

Drive Gears Driven Gears
Code   Drive Gear  Teeth   Color
 A      8628793     17     Red
 B      8628838     10     Purple
 C      8628891     19     Yellow
 D      8634934     13     White
 E      8639906     10     Green
Notice that there is 2 drive gears that are 10 tooth but different colors. I do not know the reason. Though there is a reference to an adapter of some sort that is not to common.
Code   Driven Gear  Teeth   Color
 A     25522497     45      Lt Blue
 B     25524921     28      Yellow
 C     25524922     26      Brown
 D     25524923     27      Black
 E     25524924     29      Green
 Q     25522475     34      Lt Green
 R     25522477     35      Orange
 S     25522481     37      Red
 T     25522483     38      Blue
 U     25522485     39      Brown
 V     25522487     40      Black
 W     25522489     41      Yellow
 X     25522491     42      Green
 Y     25522493     43      Purple

Remember that this is info on an 86 Cutlass. Since the car's speedo is an estimated 15+ mph high, I'll need to open it up and count gears. Since I need to slow the speedo I'll go up a few teeth on the driven gear and see.

There is also a range of compatibility between drive and driven gear. A particular size drive gear only works with a small range of driven gear size. It's highly possible that with your cars original configuration that your speedo gears are already at one end of the range or the other.

Hypothetically; Let's say my Cutlass has a Yellow drive gear indicating it has 19 teeth. I count the Red driven gear at 37. I might want to try a Black driven gear at 40 teeth to slow my speedo. Problem is my White 13 tooth drive gear only accepts up to a Blue 38 tooth driven gear. I would need to change both gears. The drive gear would need to be swapped smaller to a 17 tooth Red gear to work with the 40 tooth Black. But wait! I just sped up the drive gear by dropping 2 teeth. I'll actually need to go higher than 40 teeth on the driven gear to compensate. Phew!

So long as your armed with both your teeth count you can go to your local dealership and find out if you need change one or both to shift more than 1 or 2 teeth.

The tranny shop I deal with has all this info in a book. They can look up the gear color and tooth count etc. If you have problems with larger/smaller diameter tires, use a gear calculator, ( The MGB Experience: Tire/Gear Calculator) then use that as your final drive ratio to get the right gears. I THINK that all makes sense.

I've had good luck choosing a speedo driven gear this way;

  1. Determine what percentage the speedo is off - go 10 miles on the freeway, counting the mile markers to determine the percentage of "incorrectness".
  2. Count the number of teeth on your driven gear.
  3. Calculate the teeth count needed on the new gear. In other words, if your odometer[and therefore your speedo] is 10% slow, you need a driven gear with 10% less teeth, and vice versa.

The easier and more expensive way is to take the car to a speedometer calibration shop. They will get it right on. My car was so far off, the gear inside the transmission would have had to be replaced to change the speedometer ratio enough. It was cheaper to buy the shop's speedometer "gearbox", a little box that goes between the speedo cable and the transmission, it corrects for the error. Total cost was $100.

[ Thanks to Gary Couse, Greg Zimmerman, Dorian Yeager, Dave Brode for this information. ]

Torque Converters

Very simply put, the stall speed is when the rotor and stator in the torque converter come together as "one" to impart the full input torque to the tranny. The higher the stall, the more slip in the converter. The engine revs freer into its torque band before it imparts full torque to the trans, and well, there's books on this subject, so I'm not going to get into it here.

It is a fluid coupler, and some slip is desirable and necessary. Otherwise, you won't be able to idle in gear. Think about a manual trans for a moment. If you don't push in the clutch pedal when coming up to a stop sign, the engine dies. You uncouple the engine from the drive train. Your automatic has the slip built in to allow the engine to stay in gear at the light. Now at the same stop sign, dump the clutch at 650 RPM. Engine will probably die. Now, dump the clutch at 3000 RPM. Rubber on road. Harder launch, poorer gas mileage. Get the idea? Now at 3000 RPM, if you feather out the clutch, it won't leave as hard, because you are already imparting some of that torque to the trans and wheels. Higher stall, a better full throttle launch. I know this is a poor comparison, but if you don't have an idea about how they work, this might help a little.

The torque converter has essentially no designed affect on the shift point of the trans. It is used as a fluid coupler only. The shift point control is done by pump pressure,the governor and modulator settings, and the stiffness of the springs in the valve body. In effect, RPM, fluid pressure and vehicle speed. I suppose if you got a 4000 RPM stall converter, it may have an effect on shift points due to changing RPM/vacuum signals, etc., but if you stay within 2000-2200, it shouldn't make any difference. The governor is not affected at all by the torque converter. It is only affected by output shaft speed. The governor will need adjustments if you go from a 2.73 to a 5.14 rear gear though.

If you are racing the car, then you would like to raise that stall speed to somewhere around 2800 or so. During the race you really only need the stall from the starting line. There are two types of stall you must be concerned with. Flash stall is one of them. But that's another ball game.

I imagine you are wanting this to be a street cruiser, where, you won't be going from idle to 6000 rpm from the stop light. High stall speeds on the street should not be used. The higher the stall, the higher the trans fluid temps also, and waste some gas. Just add a tranny cooler to deal with the increased heat.

I recommend, since you have a stock cam, that you stick with the factory type stall speeds. However, if you have changed the power band with a new cam, you can realize some gains with a higher stall convertor. For example, a 2400 stall converter in an Electra with a rebuilt 403. Even with the 2.41 rear, the off-the-line acceleration improved, as the engine could get into its power band much more quickly.

Advertised stall speeds are general. Torque input has a lot to do with stall speed on the same converter. More torque, more stall. Simple as that. You need to figure out what you want to do with the car, and buy/install parts accordingly. A high stall converter alone won't make your car lightning quick. You'll need gears, consider weight, engine mods, etc.

If still in doubt, call up one of the manufacturers of torque converters. They can most likely help you determine which converter is best for your application. If you tow a boat, for example, you may want to consider a low stall speed.

For those of you who wonder how a torque converter multiplies torque, here it is. As paraphrased from a circa 1967 Petersen book called Basic Clutch and Transmission Systems. (Aren't we glad dad didn't throw this out all those years mom wanted him to?)

The torque converter is a fluid coupling which uses what basically amounts to two propellers that run in transmisison fluid. They have dozens of blades. The impeller (propeller connected to the engine) spins and pushes fluid against the turbine(the propeller that is connected to the input shaft of the trans) and causes it to spin. So far I've said nothing that most of us don't know already.

Using an impeller to turn a turbine is not technically a torque converter. The actual torque multiplication is accomplised with the stator. The blade angle of the impeller and turbine is set for maximum efficiency. The problem is that when the blades of the turbine are angeld for maximum efficiency the fluid shoots back at the impeller at an angle that slows the impeller down. The stator is a set of stationary blades mounted in a full circle between the impeller and turbine. The stator eliminates the retarding effect on the impeller. In addition, it multiplies torque by redirecting the fluid that ricochets off the turbine back toward the turbine. It bounces back the fluid that gets deflected by the turbine and increases torque. The book gives the analagy of tieing a teacup to a roller skate and then spraying a water hose at the teacup to push it down the sidewalk. Some of the water that hits the teacup is deflected back out and doesn't help to push the roller skate. It is also pushing against the stream coming from the hose. If you mounted some more teacups so that they catch the water getting deflected and redirect it in the same direction as the water spraying from you hose, the force of the redirected water combined with the stream from the hose will hit the cup on the roller skate that much harder. The end result is that you've gotten torque multiplication by redirecting the water. This is the same principle the stator works on.

The torque multiplication comes into play when the impeller is spinning faster than the turbine; under acceleration. The motor's and impeller's revs are up and fluid is bouncing off the slower moning turbine. At cruising speed when the motor is spinning just enough to keep the car moving a constant speed, the impeller are turning at nearly the same speed. All of the fluid in the torque converter housing is turning at the same speed as the impeller and turbine and the fluid is no longer deflected off of the turbine blades. The stator creates drag at this point because it's basically in the way. To overcome this problem it is mounted on a one-way roller clutch. When fluid is being bounced off of the turbine and into the stator, the clutch doesn't allow the stator to turn. But when the turbine catches up to the impeller and is no longer bouncing fluid back, the clutch allows the stator to turn with the rest of the spinning assembly and since it's free-wheeling, it's not creating any drag.

The switch-pitch converters actually change the pitch of the stator blades. The blades are either at two angles, high and low. Low angle is about 32° and high angle is about 51°. The low angle is used below about 50% throttle. Above about 50% throttle opening the stator uses the high angle. It allows for greater multiplication of torque by redirecting more oil to the impeller. The low angle allows the motor (hooked to the impeller) to spin less rpm for each rpm spun by the turbine. The low angle allows for greater efficiency at cruise speeds. The high angle engages at idle to decrease creep, since it's ineffective at low rpm. The blades are actuated by a hydraulic piston that rides in the hub of the stator. The piston is electrically controlled.

Stall Speed
Unless you have a radically modified engine, a converter of about stock stall speed or slightly higher will be fine. The only reason to run a "loose" converter is if you have a very radical cam and require a higher idle speed. The high stall will only be a benefit during drag strip launches, as it's function is to allow you to power brake the engine up to an RPM which will be in the power band. At all other times (as in, driving on the street) the high-stall converter will slip more that stock and cause a reduction in mileage. Something between 1800 and 2400 RPM stall speed would be fine.

Stall speed is not a finite thing. You can put a 2000 stall converter in a heavy (4500lb) car and it will act like a 1500 stall converter. Put the same converter in a light car (2500lb) and it will act like a 2500 stall converter. Given that its in a relatively heavy 88 I doubt you'll have any trouble. You'll build up more heat but if its cold the case will dissipate more heat and basically even things out. Now, if the converter is loose enough that when it's in drive the car doesn't creep forward then you might run into a problem. Since your cruising rpm wouldn't be high enough to fully spin up the converter it would be slipping a lot and really build up a lot of heat and give you fluctuating rpms. If you have to keep your foot on the brake at stoplights, I would say your most likely ok.

I believe a convertor rebuilder could "loosen" any convertor to slip to 3000, but it will not be very, very inefficient. I think, with an Olds anyway, that you should use a convertor built as "tight" as it can be. If you need a higher stall rpm you need to go to a smaller convertor.

I would not recommend a 10" convertor for constant street use. It's a pain. A tight TCI 10" will stall around 3800 behind a good 455 [with slicks]. I would say a tight 11" convertor should stall around 3100-3200 behind a healthy 455 [with slicks].

My personal choice for the street is a switch pitch [vp - variable pitch] TH-400 with a 12" vp Jetaway convertor. The Jetaway's 12" convertor stalls 2000/3000, as opposed to the vp TH-400's 13" convertor, which stalls 1000/2500. You can easily convert a non vp TH-400 to accept a vp convertor. It does cost a few bucks. I believe the switch pitch can be modified for more stall speed too, but i don't have any first hand knowledge there. I went from a switchpitch 2000/3000 convertor to a $275 10" 3800 TCI [non vp], and was VERY disappointed. The 3800 picked up a bit of E.T., but lost MPH.

On the VEGA convertor subject. It's been a while since i've seen any, but i think they came in two different sizes, 10" and 11", I think. I think the larger one stalls around 3000-3200 in a full sized big motor car. I think the smaller one really slips alot at partial throttle, and stalls higher too, of course. I wonder if the convertor rebuilders sell them?

When flooring the gas while holding the brake certain things may happen depending on your vehicle/engine combo. 1) The car will move forward.(more engine than car). 2) One or both rear tires may start spinning (typical). 3) The engine rpms do not go past the converter stall speed (heavy car small engine). In your case you will have to limit the engine rpms at the line so you don't roll through the lights or spend more money to prevent this.

A looser converter (higher stall) will let you see more rpms before the car moves but also builds up heat faster. It is also less efficient on the street. A trans. brake would be a logical choice if you are doing lots of racing. They lock the tranny in reverse while you have it in first gear which keeps the car from moving while you floor the gas pedal. When you release the button the tranny comes out of reverse and the car leaps forward in first. Another source of excess heat. I doubt your brakes are really bad, you are just over powering them.

[ Thanks to Mike Bloomer, Dave Brode, Dave Wyatt, Joe Padavano for this information ]

Under high torque/stall situations, it's very common for the converter to actually swell up like a balloon under the stress. It's perfectly normal. Of course this pushes everything foreward and backward respectively, and if there's no free play between the block, converter, and front pump, things will sieze up. Badly. This is, I suspect, the primary reasoning behind all the free play there.

That's also why it's recommended to stick a dab of grease in the pilot hole of the crankshaft, even on an automatic tranny'd car. The "tit" on the front of the convertor will enter into that hole upon swelling. I've heard of convertors getting stuck there before. It's rare, but happens. I've heard of that part being gouged up when someone pulled the tranny and wondering how it happened. Well, that's as good a reason as any I could make up, makes sense too.

Changing With Transmission in Car
To swap the torque converter you need to do everything you'd need to do to change the transmission. Get the car as high off the ground as you can. Drop the drive shaft. Remove shift linkage and kickdown. Drop the cross member. ((Make sure you have something holding up your engine so when you remove the cross member your engine doesn't pivot back on the rubber mounts and damage the distributor against the firewall. Engine crane and chain is best. Floor jack with piece of 2x4 under the oil pan will work too. Just don't jack straight against the pan.)) Remove the tranny and swap converters and put'er all back together. Since you'll have the tranny out anyway, that would be a perfect time to go over that also. If it's in good shape I'd at least put in a new filter and a shift kit and gasket. Takes about 20min and $25 to do that. I'd also get a pan with a drain plug at this time too. They save a mess on the garage floor.

[ Thanks to Charley Buehner, Ken Snyder, Mike Rothe, Bob Barry, Greg Pruett, Gene Gilpin for this information. ]

Transmission Crossmember Positioning

All the 1964-1977 A-body cars have multiple holes in the chassis for different transmissions. For the TH-400 you must use the most rearward set of holes for your crossmember.

The convertibles also attach different than coupes. They are (If I remember correctly) bolted on from the bottom, because of the boxed frame and the coupes mount from the top.

The 4 spd cars will have the crossmember in the same place as a Jetaway trans.

[ Thanks to Jim Chermack for this information. ]

T.V. Cable

I think I saw somewhere that GM recommends readjust that cable once a year for normal cable stretch to keep things optimum. Just one of those maintenance things no one does.

[ Thanks to Thomas Martin for this information. ]

Type F Fluid

This is a common trick that the Grand National guys do. You don't have to rebuild the trans first to put in the type F. It is compatible w/ Dextron so they say. It has less friction mofifiers then Dextron thus giving a 'harder' shift then Dextron. So in a word. Yes, you can use Type F in a GM trans.

Type F has been touted as working to firm shifts for ages. It does work, but it is not good for organic clutches. It tends to allow them to be torn easier for lack of a better description.

[ Thanks to FRank, Kerry Kroger for this information ]


The "gray silt" as it were, which looks like mud, is friction material from the clutches and/or bands. Some wear is normal, but as the silt builds, the transmission tends to slip a bit more, therefore more silt produced. A small amount seems to always be present in "normal" trannys, although if a whole lot is found, it could work it's way into the filter, clog it, and you know what that means. The factory has built in heavier springs and smaller fluid ports, etc, to SLOW the shift process somewhat, to give you a smoother shift. This means more slip as the tranny shifts. Which more wear will occur. Those street/strip type trannys and kits give you the bang shift, which, believe it or not is GOOD for your tranny. The U-joints might argue with you on this.

Transmission problems aren't always easy to diagnose, and the CERTAINLY are not easy over the internet. I'm no expert, but I've rebuilt a few TH-400's over the years, and I've seen some sick ones and good ones. The most common occurance of trans problems I've encountered is clutch burn due to overheated transmission. There is truth to the fact that you must keep an auto transmission cool at all times. Upwards of +250 degrees, and you may start to have problems. "normal" op temps for TH-400's are in the 210 degree range. I installed a cooler and trans temp guage in my 71. I put the guage in the OUTLET of the transmission, to see how hot the fluid is leaving the trans. So far the hottest I've ever seen after some hard use is 182. And it's been working great since 1992.

Probably the best way to find out what the tranny is doing is to go to a reputable (not Junky Joe's Transmissions, et al.) trans shop and ask them to do a pressure check. A guage is fitted to a threaded hole on the line side of the hydraulics (pressure plug is removed on side of trans) and a series of load tests are performed. This can tell you a LOT about the hydraulic system.

Warning. If the guy says, "Oh, I can tell without the guage," beware. He couldn't tell you what pressure you are running without the guage. He might just be trying to rebuild your tranny even if it may not need it.

It could be the thing is just wearing out. The clutches go bad, the pump, pump reilief valve, internal seals, valve body, or pressure accumulator give up the ghost, then it can cause what you describe. But, so could a vacuum leak to the modulator. A leak could "fake out" the modulator into thinking that the throttle has been mashed, and down shift. Check all vacuum lines for evidence of leaks. This is free, and not that much trouble. Ensure the fluid is at the correct level, and SMELL it and look at the color. If it is brown, or smells burnt, well, it's toast.

A few things lead me to believe it is something with the tranny. While it is cold, it shifts fine. The fluid gets less viscous (easier to flow) as it heats up, so the pressure gets lower. It happens to all of them. If the pressure gets too low, the transmission will not respond correctly. Pressure is the key. Like any hydraulic system, parts can and do eventually wear out. When you rev it, you may just be increasing the pump speed, which in turn will raise pressure, maybe enough to complete the shift, then fall back again. It also increases vacuum, so this alone is possibly a valid reason to check the vacuum line. You mention aluminum pieces. Big ones. A few "shaving particles" is normal, and expected (less than a teaspoon). A glop of them, or big chunks, as you describe, are not good. Where do you think the aluminum comes from? Two places. The case (most likely) or the clutch pistons (not very likely). Aluminum chunkies are not good. If it is magnetic, then you have some hard parts dying, and you better not drive it.

[ Thanks to Mike Rothe for this information. ]

Manual Transmission Identification

The right side of the case should have two 1" high code letters. For 1970 (and maybe other years), the three speed heavy duty transmission has 2" high ID code letters on the right hand side of the extension.

ID     Year(s)   Option   Type      Application
DA     '70       (none)   3 speed   88 column shift (5400, 6400, 6600 series)
                                    (heavy duty)
KA     '70       M-21     4 speed   F-85, Cutlass, Supreme, 442 (3200, 3600
                                    4200, 4400 series) (close ratio)
RM     '70       (none)   3 speed   442 floor shift (4400 series) (heavy duty)
RM     '70       M-14     3 speed   F-85, Cutlass, Supreme floor shift, except
                                    station wagons (3200, 3600, 4200 series)
                                    (heavy duty)
RR     '70       (none)   3 speed   F-85, Cutlass w/L-6 (3100, 3500 series)
RT     '70       (none)   3 speed   F-85, Cutlass, Supreme, Vista Cruiser
                                    (3200, 3600, 4200, 4800 series) w/V-8
TM     '73       M-15     3 speed   Omega, Cutlass
TM     '74       M-15     3 speed   Omega
WB     '70       M-20     4 speed   F-85, Cutlass, Supreme (3200, 3600, 4200
                                    series) (wide ratio)
WD     '73       M-20     4 speed   Cutlass (wide ratio)
WO  (close ratio, heavy duty)
WT  (wide ratio)

The block or bellhousing bolt pattern is the same whether AT or MT, small or big block. All MT 1964 thru 1976 Olds V-8's use the same bellhousing.

4 speeds use the same yoke as a TH-350.

According to Hollanders, ALL M-20's, M-21's and M-22's are interchangeable, even as DIRECT replacements (between roughly 63-70). The extension housing WAS different on some, but that is obviously changeable.

[ Thanks to Kurt Heinrich, Greg Rollin, Dorian Yeager for this information ]

Manual Transmission Comparison

Here are some common transmission gear ratios:

Model/Series          Gear Ratios                              Input   Groves  Cluster   Output
  (Ratio)     Years   1st   2nd   3rd   4th   5th  Rev  Final  Spline  (Input)  Pin      Spline
 M20 (Wide)   63-65  2.56  1.91  1.48  1.00   --                10      None    7/8"      27
 M20 (Wide)   66-71  2.52  1.88  1.46  1.00   --                10       1      1"        27
 M21 (Close)  63-71  2.20  1.64  1.28  1.00   --                10       2      7/8", 1"  27
 M22 (Close)  65-69  2.20  1.64  1.28  1.00   --                10      None    1"        27
 M20 (Wide)   71-74  2.52  1.88  1.46  1.00   --                26       1      1"        32
 M21 (Close)  71-74  2.20  1.64  1.28  1.00   --                26       2      1"        32

 M20 (6-cyl)         3.11  2.20  1.47  1.00   --
 M20 (V-8)           2.54  1.80  1.44  1.00   --

 5TM40 Std           3.50  2.05  1.38  0.94  0.72  3.41  3.61
 5TM40 Opt           3.77  2.19  1.38  1.03  0.81  3.41  3.61

Do a web search. Try, and enter "Muncie". This page identifies all Muncie makes for the entire run of the trans. Includes code dates, rebuild kits, comparisons to the Borg Warner, ect..

[ Thanks to Kurt Heinrich, Gene Gilpin, Paul Brillhart for this information ]



Electrical Connections

Input Shaft

Years Splines
'63-65 10-spline, no grooves
'66-70 10-spline, 2 grooves
'71-74 26-spline, 2 grooves

Output Shaft

Years Splines
63-65 27
66-71 27
71-74 32



[ Thanks to for this information ]


M-21's were factory installed in many many big block high horse GM muscle cars from 427 Corvettes to RA400 Goats to W-30 442s to 454 Chevelles. They are plenty capable of handling 500+ ft/lb torque and just as much horsepower. Just make sure your M-21 is in good mechanical condition. Like all mechanical things, get 100,000mi and countless full bore speed (and missed) shifts on a tranny and it gets worn out. Don't just throw one thats been used and abused behind your 455 expect the world. Inspect it thoroughly and if you question it at all rebuild it. At least new bearings and sychronizers.


Electrical Connections

Input Shaft

Years Splines
'63-70 10-spline, 1 groove
'71-74 26-spline, 1 groove

Output Shaft

Years Splines
63-71 27
71-74 32



[ Thanks to Gene Gilpin for this information ]


The noise that the M-22 makes is normal and has to do with the angle at which the gears mesh. You'll usually hear it in 1st, 2nd, and 3rd gear (but not 4th) after you've accelerated and you then release the gas pedal, letting the engine brake the car. It has almost the same sound in reverse. The M-22 gears have a shallower mesh angle which causes the "whine," and the sound is the reason for the popular nickname for this transmission, the "Rockcrusher." The lower angle (I believe its 11 degrees) increases the load carrying capacity of the gears at the expense of the increased noise. The reason for absence of the noise in 4th gear is that 4th is a direct output from the input (1:1 ratio), and there are no significant gears involved. The M-21 has more of an angle cut into the gears and while the ratio's are identical to the M-22 they mesh quieter. M-21's have a crusher like sound but much quieter than the M-22's and louder than saginaws. Saginaws don't make any noise until they break. Then they sound like they are going THROUGH a "Rockcrusher".

The M-22 (for Olds) was only available for one year, and it was on a '71 W-30, and had a 26 spline input shaft.


Electrical Connections

Input Shaft

Years Splines
'65 10-spline, no grooves (maincase modified for 1" countershaft pin, casting � routered off)
'66-70 10-spline, no grooves
'71-74 26-spline, no grooves

Output Shaft

Years Splines
65-69 27


1965 M-22 was '65 used a 7/8" diameter countershaft pin (unless casting � machined off), and '66, all Muncies went to the 1" diameter countershaft pin.

[ Thanks to Jeff Easton, Gene Gilpin, Mark Cornea for this information ]


Bottom line on Muncie input shaft identification:
Year Model Input Shaft
'63-65 M-20 10-spline, no grooves
'66-70 M-20 10-spline, 2 grooves
'63-70 M-21 10-spline, 1 groove
'65 M-22 10-spline, no grooves (maincase modified for 1" countershaft pin will have casting � machined off)
'66-70 M-22 10-spline, no grooves
'71-74 M-20 26-spline, 2 grooves
'71-74 M-21 26-spline, 1 groove
'71-74 M-22 26-spline, no grooves

The only difference between a M-20 and a M-21 is the gear on the input shaft and it's partner gear on the counter shaft. All of the other gears are identical. The difference in ratios is done by this initial ratio as all except 4th go through the counter shaft. 4th is a direct coupling of the input and output shafts. If you want to convert a M-20 wide ratio to a M-21, close ratio, all you need to do is swap out the input shaft and matching counter shaft, aka cluster gear, with the close ratio parts. You can also go the other direction if you wish.

Early Muncies had a 5/8 shaft that runs through the counter shaft. The later ones used a 3/4 shaft with more bearing surface. The change was made in the late 60s. Most Muncies found are the later version. The early models seem to be scarce. Probably from abuse!

First year M-22 was '65, but only a handful of units (~50-60) were produced, essentially hand-built off line at the Muncie plant. '65 was the last year for the 7/8" diameter countershaft pin, which had been identified as an area to be upgraded. The '65 M-22s had the maincase (same casting as other '65 M-20/M-21) modified to accept a 1" diameter pin, as well as the low helix angle gearset and other M-22-specific parts; in addition, the maincase had the production casting � routered off to denote that it was modified from the other production Muncie maincases. These '65 M-22s had 10-spline input shafts with no circumferential grooves; this was the same input shaft external configuration as '63-65 M-20s.

In '66, all Muncies went to the 1" diameter countershaft pin and revised input shaft groove identification with M20=>2 grooves, M21=>1 groove, and M22=>No grooves, all with 10-spline input shaft. This was continued through '70 (the ABC ratio suffix code was introduced during '69 model year; A=M20, B=M21, C=M22). From '71-74, the input shaft was changed to the 26-spline configuration for all Muncies, maintaining the same groove ID arrangement as '66-70, and the output shaft was changed to accept the TH-400 slip yoke.

New Muncie's have been out of production since the mid 70s. Borg Warner T-10s took up the slack. They can be swapped in place of a Muncie with a few accessory upgrades like the shifter and possibly a clutch disk.

Muncie also manufactured a M-22, aka Rock Crusher. It was a close ratio like the M-21. The differences are, more splines on the input shaft, straighter cut gears, and a Turbo 400 size output shaft.

They also made a hybrid with M-22 input and internals while keeping the M-20/21 output shaft. My cousin has one is his '72, low mile, one owner, all original ss350 Chevelle. He ordered the car new with an M-21 and this is what it came with. He found the odd ball tranny when he replaced the clutch. It is the only one he or myself have ever ran across, by then 4 speeds were getting rare. Therefore it is possible that you could find one of these in a '72 or newer car.

All in all Muncies are fairly "swap friendly". One other thing though, most Muncies have the speedo cable on the drivers side (left) of the tail shaft. My Olds has it on the passenger (right) side. Chevy and Pontiac used the left side style. I don't know what Buick used. The housing can be swapped for your application.

A good souce for 4 speed parts of all make is:

1710 East 29th St
Muncie, IN 47302
[ Thanks to Dave Wyatt, Jeff Easton for this information. ]


There are two distinct GM T-5 trannys - one used behind low output 6's and the other used behind 8's. The one for a 6 is rated @ 240 ft-lb and the 8 @ 300 ft-lbs. of torque. Identifiable difference is the input shaft, 14 splines on 6 cyl. version, 28 splines on 8 cyl.

1988 and newer Camaro 5-speeds are called "World Class" T-5's w/ improved bearings, paper cone syncros, and use Dextron 2 ATF. The Camaro bellhousing includes a hydraulic thowout which makes it very simple to hook up, but the b/h also tilts the tranny at an angle of about 10 degrees. This can be a benefit or a curse depending on the application.

There are also two available overdrive ratios, either .73:1 or .63:1.;

After a bit of a search, I found that a S10/S15 T5 has the shifter mounted forward compared to the Camaro/Mustang units.


Electrical Connections

Input Shaft

Output Shaft



[ Thanks to for this information. ]
Mark Sedlack [email protected] Frank Evan Perdicaro [email protected]



Electrical Connections

Input Shaft

Output Shaft



[ Thanks to for this information. ]


As far as I know, the Getrag 5-speed used in various applications are the same internally. The transmissions are made by New Venture Gear instead of GM Muncie. New Venture Gear is a joint venture between GM (Muncie transmsission) and Chrysler (New Process Gear). The information I do have is that they are the same between models. A good choice would be a J-car with a 2.8/3.1l V-6, a W-car with a 2.8l V-6, an N-car with a Quad-4. These should all be built to the same torque and horsepower specs. Before the Getrag, GM used a Muncie 4-speed and an Isuzu 5-speed in these vehicles.

Some information on the Getrag as of 1989:

HM-282 (5TM40)
200 lb/ft maximum torque
88 lbs. dry weight
7000 RPM Maximum input speed

5TM40 Standard would be for J and N cars. 5TM40 Optional would probably be W-cars due to larger tire size, and Quad-4 due to higher operating revs. Not known for sure.


Electrical Connections

Input Shaft

Output Shaft



[ Thanks to for this information. ]

Richmond Transmissions

First: the Richmond 4 speed is basically the T-10 transmittion which was stock on the late 70's cars like the Z-28 etc. It should have something like a 2.5:1 1st gear and a 1:1 final drive ratio. Richmond version has improved gears, etc, etc. Costs just over $1000 and you supply the shifter.

The Richmond 5 speed is basically a copy (they bought the rights) of the old Doug Nash 5 speed. This is a very tough street transmission with a torque rating of 450 ft-lbs with a 3.23:1 1st gear ratio. Final drive is 1:1 (5th gear). The gears are closely spaced (IMHO so closely that under light throttle you can easily skip a gear).

Richmond gear recommends a 2.73-3.05 final drive ratio and points out the 3.05 and the 5-speed will have the same gear multiplication as a 4.56 rear and a close ratio (m-21 or m-22) 4-speed - except that you have the extra 5th gear for cruising. Cost is about $1700 (Summit racing might have one design for less) you supply your own shifter - don't get the Hurst($280), get the Long shifter ($300+).

The transmission is based on an aluminum split case. Parts are easy to come by. There are some upgrades like NASCAR bearings etc. that help durability but not torque ratings. You can also get 4:1 1st gears but that reduces the overall transmission torque rating. This transmission is ment for acceleration!

Richmond gear also offers a 6-speed. It is identical to the 5-speed except it adds an overdrive. It also comes standard with all the heavy duty parts like NASCAR bearings etc. It also comes with a shifter (saves you $350 or more). The bad news, it cost about $3000. This one will give you the pressed in the seat acceleration + top speed.


Electrical Connections

Input Shaft

Output Shaft



[ Thanks to for this information ]

Manual Transmission Swapping

Olds only drilled manual transmission equipped engines for pilot bearings. In 1975, Olds began machining all engines for pilot bearings. Keep in mind that these cranks are not nodular iron like the older models, and are somewhat weaker.

This will be hard to explain. If the center of the rear of your crank has an indentation with a small shoulder about 1/4 of an inch inside you can get a pilot bearing from Mondello that drives into the rear of the crank. If the back of your crank is flat in the center you will have to have it drilled. Don't cut the input shaft. It will likely cause an out of balance situation and destroy the tranny. Or at least wear it out quickly.

The front end of the input shaft of the transmission runs in a bearing in the back side of the crank. Cutting off the tit that engages the bearing is NOT a good idea, and should not be considered an acceptable alternative! Have the crank machined for the pilot bearing.

To change from an automatic to a manual transmission, you also need a clutch, pressure plate, throw out bearing, clutch linkage, and a flywheel, and probably another starter.

You are going to have to buy a clutch and flywheel anyway. Get the Richmond Gear trans with the fine spline input. Consider the appropriate clutch from Center Force, For a flywheel get a steel SFI approved one - I personally recommend McLeod but haven't seen RAM. Check the mail order companies: PAW and Jegs for pricing.

I would not even consider using a stock aluminum bellhousing in a high output application. I've seen the results of an exploding clutch disc and I can understand why the NHRA requires a SFI spec bellhousing (scatter shield) on all cars running 11.99 or quicker. Call Jegs or Summit for the best price on a Lakewood bellhousing. As for a hydraulic clutch, check with McLeod Industries at 714-630-3668.

For manual transmissions there are the Corvette and Carmaro 6-speeds. Each of those options will set you back $2000 for purchase price, and I believe they all use electronic speedometers requiring either an adapter or a electronic speedometer. I think 4000 pulses per mile. The Richmond gear is an easier fit. You need to use the yoke from a TH-400. The cheapest place to buy one new is Strang. The dealer charges something like $120, Strange charges something like $60 for an alloy one.

[ Notice: ]Please refer to the Transmission Swapping Detail section!

[ Thanks to Greg Rollin for this information. ]


If you have a rear gear any lower (numerically) than a 3.23 I'd strongly suggest the wide ratio, M-20. Take offs are noticeably easier on the clutch. 4th is still the 1:1 so gas mileage won't really differ.

If you use 3.55:1 or numerically lower, you should use a M-20 (wide ratio), due to the lower first gear and smaller difference in 1-4th gears. If you are going to use 3.73:1 or numerically higher, use the M-21 (close ratio). Larger difference in gear ratios between each 1st 2nd 3rd and 4th gears.

If you get a M-22 to replace either the M-20 or M-21, you'll need a new clutch disk (fits on the shaft), and probably (as they tend to wear into each other) a new pressure plate.

[ Thanks to Paul Brillhart, Harry for this information. ]

Manual Transmission Tuning / General Information / Fundamentals

Clutch, Clutch Forks, Flywheel Sizes

All the Olds flywheels are drilled for both diameter clutches. Your 442 will have a 11 inch clutch. All A-body cars with big blocks had the larger clutch. The flywheels are the same for big and small engines.

350s used 10.5", big blocks used 11". You can run an 11" behide a 350 (done it) as the flywheels are drilled for both. This way, when you get the 455, the clutch will fit ('course at that point, you MIGHTASWELL get a new one...)

The Olds flywheel I had on my 67 Cutlass was drilled for both size clutches. No problem using an 11" on there.

I have been running the Center-Force "Dual-Friction" clutch for about 10 years in my 65 442. Absolutely a fantastic clutch...moderate pedal pressure, no slippage, been using it street/strip running consistent low 13's on MT street tires. I would highly endorse this clutch.

When yanked the motor out of the 67 442 the little pivot point that screws into the block broke off. Went to the dealership to try and get one. They discontinued the Olds part years ago. I had him look up a 1970 Chevy pickup clutch pivot. They still make that one, and upon inspection it turns out its the exact same part. Chances are if the pivot is the same and the throw out bearing is the same, the lever will be the same. It's amazing they dont cross reference these things.

But on the other hand, I went through this a year ago on my 71 442, the clutch fork isn't the same across all the GMs, definitely different for Chevy's, might be the same across BOP. I ended up getting the fork from Ken Reese in Florida, cost $60, after I first tried the Chevy fork. You are correct that the pivot point (which simply screws into the bell housing) is the same but the fork is not. The difference in the forks is subtle, maybe a quarter inch or so but after installing it you'll see that the throw out bearing isn't centered on the clutch "fingers".

[ Thanks to Todd Morris, Jim Chermack, Joe Padavano, Chris Witt for this information ] [email protected]

Converting to Hydralic Throw-out Bearing

My brother did this. Major pain in the ass. The master cylinder is mounted to the pedal bracket. This will no way fit under your exsisting power booster (if you have one). We had to move the master off of the bracket and make all sorts of stuff to make it work. It works good but took ALOT of time and trial and error. This was the setup from Summit maybe there is some thing different out there. I was once looking into changing it to a cable like some new cars. I think this would be alot easier.

[ Thanks to for this information. ]
[email protected]


The only racing (SFI certified) flexplates that I'm aware of for an Olds V8, are a "solid" construction. This type of flexplate is not recommended for street applications. As a flexplate needs to do just what the name implies. Flex. The flexplate acts as somewhat of a cushion between the torque converter and crankshaft. Since the oil pressure of the transmission is trying to force the torque converter forward, this flex cushions the natural back and forth movement of the crankshaft on acceleration/deceleration. Without any give in the flexplate, the life of the thrust bearing and crank thrust bearing surface will be reduced.

[ Thanks to Greg Rollin for this information. ]


First, the 67-69 AT shifters and consoles are all the same, so a 69 console is the correct one for a 67. The only minor difference is that in 69 the backdrive linkage was added to lock the shifter in Park with the ignition key off. While this doesn't effect the operation of the shifter in your 67, the selector plate on the console, will say "PARK/LOCK" on the 69 console instead of just "PARK" on the 67-68 units.

The 64-69 cars used a console with the shifter handle offset to the driver's side; the console and non-console cars used the same shifter handle (though the 64s were different, with a round handle, and in the later cars, the 442s had the numerals stamped in the handle, while non-442s obviously did not). The 70-72 console-equipped cars use the offset handle (actually, the offset is in the shifter mechanism; the handle is almost straight) to line up with the center of the console. I used to own a 72 442 with 4 spd and no console (but with bucket seats) and that car used the same offset shifter as the console cars.

Hurst Shifter
Don't know about production numbers, but all 69 Olds A-bodies (in fact, all 65-72s, at least) used Hurst shifters from the factory on the Muncie four speed cars. The 442s received a stick which had "442" and the Hurst "H" stamped on it, while the non-442s only got "Hurst". A lot of these cars may have been converted or had the shifter replaced with an aftermarket Hurst unit over the last 30 or so years. The way to tell is to remove the boot and look at the shifter mechanism. The factory and aftermarket units are the same with one easy to spot exception - only the aftermarket units have the overtravel stop bolts. In addition, the factory shifters used a snap-in stick, whereas the aftermarket units for the most part used a bolt-on stick (though I'm not sure if all aftermarket units are bolt-on).

In addition, the optional heavy-duty Dearborn (aka Ford Toploader) three speed also came with a factory Hurst shifter, again with a "442" stick in those cars or a "Hurst" stick in lesser A-bodies.

I've not installed an aftermarket shifter in the stock console, though I've often thought about putting a dual gate in one. I think your best bet would be to find a 70-72 factory shifter mechanism, but use the top plate from the GTO dual gate shifter. The Poncho plates were rectangular (verses the tapered plate used on the 70-72 Olds units) and IMHO would look better on the 67-69 consoles. You'll obviously need to modify the current console top plate, or even fabricate a new one.

Something I have done is adapt the 68-ish GTO automatic shifter (non-dual gate) to this console. These units have a cylindrical stick with a knob and when used normally function like any other AT shifter. They have the neat feature of allowing single gear upshifts when pushed to the right and forward. A ratchet-like pawl in the shifter mechanism positively stops the shifter in second on the 1-2 shift and in third on the 2-3 shift. The best part is that this shifter will fit the stock top plate on the 67-69 consoles with no modifications. I did this on my first car, a 68 Vista Cruiser to which I added buckets and a console (and 442 emblems and grille and a 425...).

[ Thanks to Joe Padavano for this information. ]

Table of ContentsIndexAcknowledgements

Transmissions • DiffsBrakesSuspensionSteeringCamsCarbsInterchange
Best BBBest SB260303307324330350371394400403425455Diesel
RebuildingBuildupSwapRestoreOption CodesWheelsIgnitionComp Ratio
The W'sThe H/O'sThe 442'sToronado88 / 98 / StarfireCutlassJetfireWagons
Basic Tech How ToMiscellAll VehiclesAdditional Information

 Rocketeers have navigated these pages (since April 10, 2000).

© 1996 - 2000 by the members of the Oldsmobile Mail List Server Community. All rights reserved.

Submit corrections and additions to this information to The Olds FAQ Compiler.