Muncie 3851325, 64 or 65?

[Lawrence Parisotto]

One for the Muncie experts. How can you tell the difference between a 64 and 65 3851325 main case, or more specifically, a late 64 and 65? From what I understand, the 64 main case had the date code (Pxxxx) stamped on the lower right of the side cover flange, while the 65 had the date code stamped on the passenger side of the rear flange. But when did this change occur?

I have a late 64 (June 29, 1964) build date that had a Powerglide that I'm replacing with a M20 wide ratio during restoration. I'd like to find a 3851325 main case, but not sure where the date code should be given that a lot of things seemed to change on a late 64 car. I happened to find a 3851325 tranny (date code P0729, cast 1st week July) with wide rib tail shaft and correct side cover for a good price and could swap the main case during rebuild.

Also, I thought I read somewhere that the top rear main case bolt had a rounded boss for 64 and square for 65. Is this also a way of telling the difference?

Thanks in advance,
Lawrence

[Wayne M.]

Re: Muncie 3851325, 64 or 65?

Lawrence -- You're on the right track. Somewhere between 11-25 and 12-04 of 1964 is when the top rear case bolt boss went from having a round front to a larger square one. So if your prospective 325 case P0729 has a square boss, it's 29 July 1965.

Assembly dates for all '64 Corvette trans I've seen have the code stamped on the lower right side cover corner, as you've noted. I believe that, starting with the 1965 model year, there was a general directive to stamp on the passenger side rear vertical flange of the maincase. It was probably thought that since this surface was rough cast, and not very wide, that machining should be done to prepare the surface for the assy. stamp. This was before the tail case was attached (probably before assembly was begun). The earliest "grind" I found is P0812 (1964), and they continue until at least P0917 (the assy date on Corvette 51014xx).

[Lawrence Parisotto]

Re: Muncie 3851325, 64 or 65?

Thanks Wayne - that helps. Think I know what I'm looking for now...

Lawrence