Transmission ID

[Michael J.]

In looking over the tranny on my '67, it has none of the identifying marks to indicate it is original. There is no VIN derivitive stamped on the right side, and no date stamped on the left side. The only marks are the casting number (3925660?) and some wording including "General Motors". Attached is a photo of the right side case. This casting number I can't ID, anyone know what it means? Thanks for any help.

[Joe L.]

Re: Transmission ID

In looking over the tranny on my '67, it has none of the identifying marks to indicate it is original. There is no VIN derivitive stamped on the right side, and no date stamped on the left side. The only marks are the casting number (3925660?) and some wording including "General Motors". Attached is a photo of the right side case. This casting number I can't ID, anyone know what it means? Thanks for any help.

Michael-----


The 3925660 case casting number was used for virtually all 1968-70 Muncies. So, the tranmission is likely from this period. If there are no stampings on the case, at all, this might indicate that the case was a SERVICE piece or, possibly, even a complete SERVICE transmission (although they usually have a production code stamping.

[David L.]

Re: Transmission ID

In looking over the tranny on my '67, it has none of the identifying marks to indicate it is original. There is no VIN derivitive stamped on the right side, and no date stamped on the left side. The only marks are the casting number (3925660?) and some wording including "General Motors". Attached is a photo of the right side case. This casting number I can't ID, anyone know what it means? Thanks for any help.

The 3925660 maincase casting number was used on 1968 & 1969 Muncies and possibly very early 1970 Muncies. The 1966 & 1967 Muncies used the 3885010 maincase. The sidecover casting number is 3884685 on the 1966-1968 Muncies and 3950306 on the 1969 Muncie.

[Michael J.]

Re: Transmission ID

Thanks for the help, guess this was a service replacement early in the cars life. Lucky the NCRS judges don't score originality and numbers match on trannys.

[Jim T.]

Re: Transmission ID

Thanks for the help, guess this was a service replacement early in the cars life. Lucky the NCRS judges don't score originality and numbers match on trannys.

If it is a 1970 replacement I believe 1970 was the first year for the main cases to have an drain plug for the standard manual transmission for Corvettes. Also the first year for the M20 4-speed manual at no cost replacing the 3-speed manual as standard equipment.