Repair Pontiac Mid-size 1974-1983 Repair Guide




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Fig. Fig. 1 Manual transmission ID number locations

The Pontiac mid-size models covered in this guide have been equipped, through the years, with various types of manual transmissions. A three-speed Saginaw-built transmission (both floor and column shift versions) was available from 1974 through 1976 in 250 six-cylinder, 260 V8 and 350 V8 (LeMans only) cars. A three-speed Muncie has also been available from 1974 through 1981. Both Saginaw and Muncie-built four-speed transmissions have been offered through 1979, and a five-speed Muncie was available from 1977 through 1978.

All manual transmissions covered here can be identified by checking the markings on the right side of the gearbox case. The numbers stamped on the case should always be used when ordering replacement parts or inquiring about service.


Various GM Turbo Hydra-Matic (THM) automatic transmissions are used in the models covered in this guide. 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.

The 1974 through 1976 automatics were designated either M-38 or M-40; the M-38 models were used on all six-cylinder through 350 V8-equipped cars, and the M-40 transmissions were used behind the big 400 and 455 V8s. From 1977 through 1983, the automatic transmissions available in Pontiac mid-size cars have been the THM 200, THM 350 and THM 400. Generally, the 200 series are available in four-cylinder, 231 V6, 301 V8 and 305 V8-equipped cars; the THM 350s are found in 231 V6 through 403 V8 cars; and the THM 400s are found behind various small-block (301) through big-block (455) V8s. However, always check the transmission I.D. numbers, as many different engine/transmission combinations have been used.

A quick way to visually identify the transmissions is to look at the shapes of the pans. The M-38 and THM-350 have a squareish pan with the right rear corner cut off. The THM 200 pan is similar but more rectangular. The pans of the M-40 and THM 400 transmissions are irregular-shaped. See for pan illustrations.

The 200 model transmission was first used in 1977 and is the first all-metric unit built by GM in the U.S. This transmission sometimes has the word METRIC stamped on the pan.