Turbo-Hydramatic 425
Turbo-Hydramatic 425 (TH425 or THM 425,[1] later 325) was an automatic transmission developed and produced by General Motors. The THM425 was based on the design of the THM400, with most parts being directly interchange and some others being interchangeable with minor modifications.[2] In the THM 425, the internal parts spin the opposite direction; for example, the helical angle of the planetary gears is "reversed" and the one-way clutches freewheel in the opposite direction, for example. [3] The THM425 was developed for the 1966 Oldsmobile Toronado and the 1967 Cadillac Eldorado. After the 1978 model year, both lined replaced the THM425 with a lighter-duty transmission known as the THM325 (using components sourced from the THM200). Starting 1979 and onwards, all longitudinal engine front-wheel drive vehicles used the THM325. In 1982, an overdrive was added to the THM325, turning it into the THM325-4L (4L means 4 forward speeds, Longitudinal).[4] Production of this transaxle continued until around 1985/1986, eventually being phased out, when GM moved to transverse-engine FWD layouts, and all vehicles using the THM325-4L switched to more-conventional transverse engine mounting in 1986. THM325's bellhousing pattern (arrangement of bolt holes and shape of the transmission’s engine-side mounting flange) used the 1967-90 Buick-Oldsmobile-Pontiac-Cadillac V8 pattern throughout its entire lifecycle. .jpg){kind=spacer} Vehicles that used the THM 425/325:
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