Positraction - What do I have?

[Rick F.]

I just remover the P-case from my 1961 Corvette. The case number is 3789812. The date code is H275. After looking at the "Chevy By the Numbers" and the "Corvette By the Numbers" books, as well as the many posted messages already on this forum, I'm confused.

All the information I have reviewed suggests that the 3789812 P-case (thin letter) was for 61-64 Corvettes. If that is the fact, why do I have a 1965 dated case? I have throughly wire brushed and clean the date code, and there is no doubt that it reads H275. Thanks for the help. //Rick//

[Joe L.]

Re: Positraction - What do I have?

I just remover the P-case from my 1961 Corvette. The case number is 3789812. The date code is H275. After looking at the "Chevy By the Numbers" and the "Corvette By the Numbers" books, as well as the many posted messages already on this forum, I'm confused.

All the information I have reviewed suggests that the 3789812 P-case (thin letter) was for 61-64 Corvettes. If that is the fact, why do I have a 1965 dated case? I have throughly wire brushed and clean the date code, and there is no doubt that it reads H275. Thanks for the help. //Rick//

Rick-----


The GM #3789812 case was used for L1961-62 Corvettes with positraction as well as 1962-64 full size passenger cars with positraction. It was not used for 1963-64 Corvettes.

The 3789812 case was not used after 1964 for cars. As far as I can tell, it was not used for any light truck applications, either. So, that means if you have a case that was cast in 1965 it started life as a SERVICE case. The case was manufactured for SERVICE well after 1964, finally being discontinued from SERVICE in 1983.

By the way, for SERVICE I believe this case was used for both posi and non-posi applications. If so, the "guts" of the unit you have might not be positraction.

[Rick F.]

Re: Positraction - What do I have?

Joe, Thanks for the response. This unit has a 4:11 posi. //Rick//