Chevy Manual Transmission Identification

Go here for info on Chevy Automatic Transmission Identification Muncie (left) Saginaw (center) Borg Warner (right) To quickly finger what you have, notice in the above picture: The muncie reverse lever is in the extention housing, and the cover has 7 bolts. The Saginaw reverse shift lever is on the cover, and the cover has 7 bolts. The Borg Warner has a 9 bolt cover. Muncies are the hot tip, since they usually were used with high performance engines. Again on the muncie, and looking at the cover, 3rd/4th gear lever is on the left. 1st/2nd gear lever is on the right. Further Muncie identification 3 Muncie 4 speeds were offered. The M-20 wide ratio, the M-21 close ratio, and the "Extra heavy duty close ratio" M-22, also known as the "Rock Crusher". The M-22 was generally installed behind severely powerful (high torque) big-block engines. The M-22 is distinguished from an M-21 by the angle of the gear teeth. The M-22 has "straight cut" gears. Due to this, the box tends to be noiser (whines or howls almost like a blower, which is why it's called a "rock crusher") than other boxes. The M-21 has a higher pitch angle on its gear teeth. The close ratio gearboxs generally came with 3.73+ gear ratio'ed cars. 3.55 geared and higher (numerically lower) cars used the wide ratio gearbox. Due to the wide combination of id's, stampings, numbers, etc... varied and even GM couldn't keep track of what was what, it's best to ID your gearbox visually, taking what is stamped on the box FWIW. The best way to ID the transmission is to count teeth.

Effective October 21, 1968, an additional letter was added to the plant prefix number to help identify the gear ratios in Muncie transmissions. The additional letter codes as follows:

Of course like engines, transmissions come and go over time, so below is the (as complete as I can make it) transmission plant prefix list: