Muncie (left) Saginaw (center) Borg Warner (right)
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.
