See Figures 1, 2, 3, 4 and 5
All Cadillac models covered in this guide use various GM Turbo Hydra-Matic (THM) automatic transmissions and transaxles. Transmission identification numbers are found on either side of the transmission case, depending on model. Some models also have I.D. numbers stamped on the governor cover or the number may be ink stamped on the bell housing. The Eldorado and Seville front wheel drive models (through 1985) have the identification numbers to the rear of the vertical cast rib on the left hand side of the transaxle housing. For 1986, the transaxle identification number is stamped into the horizontal cast rib on the right rear of the transaxle housing.
Cadillac rear wheel drive models may be equipped with any of the following: THM400, THM350, THM350C, THM200, THM200-4R and the THM200C transmissions. Cadillac Eldorado and Seville models use the THM440-T4, THM425, THM325, and the THM325-4L transaxles.
A quick and easy way to identify the transmissions/transaxles is to look at the shapes of the pans. Use the illustrations of the pan gaskets to help determine your particular transmission/transaxle.