What do I have??

Discussion in 'VIN, Trim Tag & Drivetrain Decoding' started by TX79Z28, Jun 27, 2014.

  1. TX79Z28

    TX79Z28 Veteran Member Lifetime Gold Member

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    I have searched the forum, looked at the data page, looked at other sources, but I am confused.

    I just purchased a rear end and I was told it was a 3:42 posi, but not specific as to what it came out of. The seller took it off a 78 Camaro, but he built that car from several cars.

    The stamped number on the axle tube is a 2 (maybe..really chopped off and offset) followed by PY G314 1

    The cast part number is 1254333, it also has what I believe to be the date stamp K68

    Another cast number GM30

    It SEEMS to have been produced in 1978, but the stamped axle code is missing the posi code (after the PY G314 1)

    I found information that the PY code was used on some late 70s Firebirds, is this what I have?

    Ultimately, how can I find out if maybe somewhere along it's life, someone changed out the gears and differential, and just kept the housing?

    Can someone help, and maybe post pictures of what a posi vs an open diff look like?
     
  2. Gary S

    Gary S Administrator Lifetime Gold Member

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    PY is a 3.42 posi used on Camaro and Firebird. That is what was originally inside this one. Until you open it up, you don't know what is inside it today.
    Posi will have clutches inside and a large S shaped spring to preload the clutches. Non-posi will have just the spider gears without those extra parts the posi has.
     
  3. TX79Z28

    TX79Z28 Veteran Member Lifetime Gold Member

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    Thanks Gary, I will open it tomorrow. Did I read the decoding page correctly? It states there should be a letter after the PY G314 1 indicating who made the posi? (Eaton etc) or maybe because this one may have come out of a firebird?
     
  4. Gary S

    Gary S Administrator Lifetime Gold Member

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    The manufacturer codes were used on early posi's made by Eaton, Warner, and others.

    The 8.5 rear end like yours used the GM Traction Lock posi unit, so there was no need to identify the manufacturer anymore on the housing.
     
  5. TX79Z28

    TX79Z28 Veteran Member Lifetime Gold Member

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    Thank you. If anyone can post a picture (of the inside of the carrier) of posi and open 8.5s, I would really appreciate it.
     
  6. Gary S

    Gary S Administrator Lifetime Gold Member

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  7. Camaro-Chevelle

    Camaro-Chevelle Veteran Member Lifetime Gold Member

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    410408 is the casting number for a 3 Series Traction Lock S-Spring Posi
    and 410409 is the casting number for a 2 Series Traction Lock S-Spring Posi.
     
  8. TX79Z28

    TX79Z28 Veteran Member Lifetime Gold Member

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    This is what I have:

    [​IMG]

    Casting 410408:

    [​IMG]

    Is a 2-series better or worse than a 3-series?
     
  9. Gary S

    Gary S Administrator Lifetime Gold Member

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    The series 3 is more desirable for most people. It was used with 2.73 to 3.73 gears. The series 2 was used with 2.41 and 2.56 gears which are great highway gears, but lack for performance.
     
  10. TX79Z28

    TX79Z28 Veteran Member Lifetime Gold Member

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    So that would tend to back up the "PY" code. As long as gears are original
     

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