Transmission general data
The
THM425 (and later 325) is a 3-speed automatic gearbox designed and released by
GM. The structure of the THM425 is based on the THM400; most spare parts in
these gearboxes are directly interchangeable and some others can be adjusted
with the help of slight modifications. The THM425 was designed for Oldsmobile
Toronado and Cadillac Eldorado.
Number of gearsTransmission TypeDriveTorque (Nm)ATF (full capacity) LATF (change) LATF type3ATRWD12,36Dexron II
More lightweight gearbox THM325 took the
place of the THM425 in both car ranges in late 1978. Since 1979 and later longitudinal
engine FWD cars have been equipped with the THM325. The THM325 was upgraded to
THM325-4L with an overdrive added in 1982, but all cars with this gearbox
switched to more-common transverse engine mounting in 1986.
How to repair this transmission (Videos)TH-400 rebuild part 1TH425 Governor Gear RemovalTH400 Rebuild: Governor