10-19-2003, 06:43:00 PM
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.
10-19-2003, 08:19:00 PM
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.
10-20-2003, 12:22:00 PM
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?
10-20-2003, 03:18:00 PM
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.
10-20-2003, 03:22:00 PM
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.
10-26-2003, 11:07:00 AM
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.
10-26-2003, 04:23:00 PM
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.