I'm trying to identify this tranny. I need to replace the front and rear bearing, but I have to know what it is before I can get a repair manual for it.

Its a cast iron 3speed with casting #'s M21 3952645. The stamped # is S2D05 and first 3 vin #'s are 12L.

So far I figured out that its a 1972 tranny, but many websites say "S" is used for muncie and Saginaw for '72.

Thanks,
Rich

I find that same confusion about the "S" code being used for both Muncie and Saginaw. I don't think we can identify the tranny from that.

3952645 shows up as the sidecover casting number for the 1972 Saginaw 3 speed. It is a cast iron case tranny with either a 2.85 first gear or a 2.54 first gear.

Chevy also had a Muncie 3 speed that year, but the side cover casting on that one should be 3952646. It is also a cast iron case. This Muncie would have been a low production tranny because it was available only in Chevelle, and probably other GM A body cars.

I did come across a site that mentioned that '71-79 3 speed manuals starting with "S" were muncie and pre '71 with "S" were saginaw.

Gary S. were did you look up the casting numbers?

Alan Colvin's book, Chevy by the Numbers has all this casting information and decoding. My set is like my bible for this stuff. I have not yet found any mistakes in his books.

Well, you right on the money. I barrowed a chiltons repair manual for '70-76 and it is a saginaw - muncie's 3spd bolt pattern is slightly different. I'll have to pickup a copy of that book you mentioned.

Thanks,
Rich

Gary,

The numbers I reported were off of the side cover and not the case. I say this because the cover is not original to the tranny - it has a reverse light switch on the 2/3 gear fork not the 1/2 gear fork! Oh well it works, just no reverse lights.

The Saginaw with the 3952645 sidecover goes with a 3925647 main case casting, and a 3873886 tail housing casting for 1972.

The Muncie that year had the 3952646 side cover and a 3911940 main case along with a 3911942 tailhousing.