Identify General Motors' Four-Speed Transmissions Jun 13, 2017While the four-speed manual transmission was a staple in many Chevrolet musclecars, even many of the General’s “other” car models were equipped with a manually-operated gear selecting device. However, finding one of these transmissions now at a swap meet or salvage yard is getting harder and harder. How to identify chevrolet gmc manual transmissions Use the following information to compare physical description of your Chevrolet or GMC manual transmission in order to identify what model transmission is in your vehicle. We offer quality rebuilt manual transmission, parts and rebuild parts kits that are designed to be top of the line. List of GM transmissions - Wikipedia Automatic transmissions Early models. The GM Hydra-Matic was a success and installed in the majority of GM models by 1950. Through the 1950s, all makers were working on their own automatic transmission, with four more developed inside GM alone.