The Turbo-Hydramatic (THM) series was developed to replace both the original Hydra-Matic models and the Buick Dynaflow. The first G.M. transmission to hold the moniker was the Turbo-Hydramatic 400, first used in the 1964 model year in Cadillacs. Now available primarily, in many forms as rebuilt transmissions.

The Buick version, which followed shortly thereafter, was known as the Super-Turbine 400. By 1973 THM trade-name transmission had replaced all of GM’s previous automatic transmission line. Some may remember the Chevrolet Powerglide, Buick Super Turbine 300, Oldsmobile Jetaway, etc..

From the early 1980s onward, it was progressively replaced by later four-speed and five-speed automatics which evolved into the T-700R4 overdrive transmissions with 4 and five forward gears, Most of them continue to use the “Hydramatic” or more precisely the Turbo Hydra Matic or T for short, trade-name.

Although the Turbo-Hydramatic name is a relative to the first fully automatic transmission. Hydramatic was actually developed and first developed and used by General Motors Cadillac division in the late 1930s, the two transmissions are not related mechanically in any way.

The last TH transmission made, about 1992, ironically was the T-400. Which can be purchased in abundance very affordably as a rebuilt transmission. A favorite of drag racers for ever, it seems, due to it’s tremendous durability. Call GotTransmissions.com at 1-888-344-8044 for a quote.