Some history of GM FWD trannies

[JasonA]

I found this on a Pontiac site and thought it was interesting. I actually know Steve Ochs from a different Internet forum (an Oldsmobile G-body forum):

Here is the rough lineage of the 4T65-E:

Designed Yr.- Production Yr.- Model

1974 - 1978 - THM-125 (3T40) - Some bushings & bearings carried from

THM-200, some basic designs of splines & shafts from THM-200 and THM-350

1980 - 1983 - THM-440T4 (4T60) - Four speed version of THM-125. Some parts

identical or very similar. Somewhat stronger than THM-125.

1983? - 1986? - F-7 - Made exclusively for Cadillac Allante. Similar

design but many parts different to improve torque capacity. More

expensive.

1985 - 1988 - 4T60-E - (F-31) Electronic shift version of THM-440T4. Most

parts identical to THM-440T4.

1991? - 1993? - 4T60-E HD - Same as 4T60-E except with a few heavy duty

parts (mainly final drive gearset) for supercharged 3.8l V-6 application.

1992 - 1997 - 4T65-E - Very similar to 4T60-E with many common components,

but many major differences also.

Below is a synopsis of a previous post with more description of changes

between models:

A little history on the 4T60 used in FWD GM vehicles.

Best viewed fixed font.

The THM440-T4 was introduced in 1984 on the new GM

full sized luxury vehicles (Oldsmobile Regency 98, Buick

Park Avenue, Cadillac Sedan Deville - remember the logo

on the trunk lid "4-Speed Automatic"). This transmission

was basically the THM125-C with an overdrive added on.

The original 440 was not very reliable. Many changes

were made the first 3 years. Areas that suffered many

failures were torque converters (clutch rivets), 2nd

clutch housings, 4th clutch area, final drive.

When the Cadillac Allante was introduced, the 440

would not handle the torque of the V-8, so a special

version known as the F-7 was developed. It included

special sprockets, heavy duty final drive, special

fourth clutch, etc. A rare but solid transmission if

you can find one.

By 1988 the quality was better, but to make the

440 (now called the 4T60) a world class transmission,

electronic controls were added. The new transmission was

coded F-31 and became known as the 4T60-E. The 4T60-E was

phased in from 1988 to 1990. You can tell by looking at

the bottom oil pan - it will be stamped with "4T60-E".

This transmission has much better reliability. By the

1991 model year, all FWD Overdrive transmissions were

the 4T60-E model.

As a side note, with the introduction of the

Northstar V-8s, a new low volume transmission was

developed for these applications. It is known as the

4T80-E. Very durable but very expensive, about 80%

higher in cost than the 4T60-E. Also 60 pounds

heavier.

With the introduction of the Supercharged 3800,

a few modifications to the 4T60-E were made. The

biggest change is the final drive unit, which is of

heavy duty design. The transmission still can't

handle the full torque of engines such as the SC 3800

and the DOHC 3.4L V-6s at redline during shifts. GM

utilizes Engine Torque Management to maintain

reliability. This consists of controlling engine rpm

and engine torque (through timing and fuel) during

shifts. That is why the SC 3800 and DOHC 3.4L do

not shift at redline at WOT.

For the 1997 model year, GM introduce the 4T65-E.

This transmission is a heavily reworked 4T60-E design

which includes such features as a 258mm torque converter

instead of 245mm, twin chains and special sprockets for

noise, Electronic Line Pressure (ELP) for ECM control

of pump pressure to better regulate shift quality,

revised fourth clutch, revised second clutch housing,

and many other improvements to reliability. The first

applications to receive the 4T65-E will be the

SC 3800 V-6 and the DOHC 3.4L V-6 to minimize the need

for torque management. The phase in will be three

years and will be complete by model year 1999.

The biggest cause of failure of the original

4T60 (440) is heat. [snip of restricted info] Through

control of shift points and torque converter lockup,

tranmission temperature can be controlled. There is

a temperature sensor in the transmission for the ECM

to monitor. This shows the STRONG recommendation

to add and external air/oil transmission cooler

for 4T60 (440) equipped vehicles.

The following is a list of GM FWD transmissions

and their applications:

Model Years Current Application

--------------- ------------ ---------------------

THM125-C (3T40) 1979-2002 J (possibly to 2002)

4T40-E 1995-future J,N,P-90

THM-440T4 (4T60) 1984-1990 None

4T60-E 1988-1999 All except J,N,P-90

4T65-E 1997-future SC 3800, DOHC 3.4L

4T80-E 1992-2002 Northstar

Steve Ochs aka N8TYS- Mfg. Engineer - GM Powertrain - Parma Plant

Transmission Division (4T60/65-E) -

The statements and opinions expressed here are NOT an official

statement of General Motors or the GM Powertrain Division