Muncie Transmission Identification

[Donald Morfield]

I would appreciate help in identifying a Munice 4-speed transmission. The top of the main case is stamped DW 0 C106604. The side of the main case has casting numbers 3885010 and 3 9 Ø 6. The shift cover plate has cast number 3884685, with a stamped metal (ratio?) tag number 3870372 attached. The number/letter stamping between the main case and tail shaft is P 7 R C 5. The tail shaft casting number is 3857584GM.

I believe the main case casting number suggests it is a 1966 or later, perhaps from a Corvette or another GM application? I haven’t been able to determine whether is a standard wide-ratio, close-ratio, or heavy duty close-ratio. Please help me understand what I have. Thanks.

Donald 8369

[Joe L.]

Re: Muncie Transmission Identification

Donald-----

The transmission components that you describe are relative to a 1966 or 1977 model year Muncie. However, the transmission code you mentioned would identify this as a transmission used for the 1967 model year. It was manufactured in October, 1966 for the 1967 model year.

I can't find any record of the 3870372 part number. However, there are many Muncie part numbers that have been "lost in antiquity". This transmission may or may not have been originally installed in a Corvette. No matter, though, since the Corvette and non-Corvette Muncies were really the same except for, perhaps, a few small details.

From the information which you've provided, I can't tell you whether it's an M-20, 21, or 22. However, by 1967 the "ring" method for identifying transmission model was being used. If the transmission still has its original input shaft or a GM replacement, then you can identify it as follows: look on the input shaft for the presence of circumferential machined groove(s) ("rings") around the splined area. If there are 2 grooves, then it's an M-20 wide ratio; if there is one groove, then it's a close ratio M-21; if there are no grooves, then it's an M-22 HD close ratio. In the latter case, check to see if there is a drain plug installed on the lower boss of the case and check the internal gears by removing the sidecover. That's because if a non-GM replacement input shaft was ever installed, it will have no rings regardless of which transmission it is.

[Donald Morfield]

Re: Muncie Transmission Identification

Joe--
Thanks for confirming my suspicion that I have a 1966-67 Muncie,decoding the date stamping, and offering a means of determining the ratio.

[Verne Frantz]

Re: Muncie Transmission Identification

Donald,
I believe your trans was originally installed in a passenger car built at the Atlanta, GA plant (Doraville). The "C" was the Plant code and the 106604 was the VIN derivitive of the car (the 6,604th car off the line that model year, at that plant).
Verne.