Muncie or Saginaw 3sp

Discussion in 'Transmission & Driveline Topics' started by malducci, Oct 19, 2003.

  1. malducci

    malducci Veteran Member

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    Oct 2, 2003
    tucson,az
    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
     
  2. Gary S

    Gary S Administrator Lifetime Gold Member

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    Apr 14, 1999
    Bismarck, North Dakota
    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.
     
  3. malducci

    malducci Veteran Member

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    Oct 2, 2003
    tucson,az
    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?
     
  4. Gary S

    Gary S Administrator Lifetime Gold Member

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    Apr 14, 1999
    Bismarck, North Dakota
    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.
     
  5. malducci

    malducci Veteran Member

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    Oct 2, 2003
    tucson,az
    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
     
  6. malducci

    malducci Veteran Member

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    Oct 2, 2003
    tucson,az
    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.
     
  7. Gary S

    Gary S Administrator Lifetime Gold Member

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    Apr 14, 1999
    Bismarck, North Dakota
    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.
     

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