Turbo-Hydramatic 440-T4
A breakdown of THM440T4 is: Turbo HydraMatic Model 440 - Transversely Mounted - 4 Speed Fully Automatic transaxle.
A 4-speed transaxle which replaced the 125, was created for the 1985–1986 GM C platform (FWD)/GM H platform (FWD) cars, the Turbo-Hydramatic 440-T4. Virtually no internal parts were shared with the 125, and overdrive was achieved by departing radically from the standard single Simpson compound planetary gearset's common sungear layout. This transaxle was first used in GM's 1985 Buick Park Avenue, Oldsmobile 98, and Cadillac Deville. In 1986, after switching to FWD, the Buick LeSabre, Oldsmobile Delta 88, and later, the Pontiac Bonneville also used this transaxle. The 440-T4 was later renamed the 4T60 under GM's new transmission naming convention. A heavy-duty version of the 4T60 called the 4T60-HD was used in the 1989-1990 Pontiac Grand Prix with the turbocharged engine. GM started adding electronic controls to the 4T60 in 1990 with the Cadillac Allante carline's unique F7, and after 1991 with the corporate 4T60-E.
One unique feature of this transmission is its use of both a modulator valve and a throttle valve (TV) cable. Most transmissions either use one or the other to control shift points and shift smoothness. On the Turbo 440-T4, the TV cable exclusively controls the shift points, while the modulator valve controls the shift feel. This feature makes it very easy for a home, "shadetree" mechanic to adjust the transmission shift points with minimum effect on the shift feel.
The 440-T4 was originally slated to be used with downsized C body cars for 1984, however, issues with failures due to lack of fluid lubrication to critical clutch train parts in the relatively complex and compact design, led to introduction of transverse FWD 4-speed automatics being delayed as an option until 1984 for the 1985 model year.
Applications:
- 4T60
- 1988-1994 W-Body
- 1986-1993 H-Body
- 1985-1993 C-Body
- 1985-1993 A-body
- 1988-1990 Buick Riviera
- 1988-1990 Buick Reatta
- 1985-1990 Cadillac models
- 4T60-HD
- 1989-1990 Pontiac Grand Prix (Turbo Only)
- F-7
- 1987–1992 Cadillac Allanté
Read more about this topic: Turbo-Hydramatic 125