different width rear ends in 73

Discussion in 'Transmission & Driveline Topics' started by Ruthead, Sep 8, 2021.

  1. Ruthead

    Ruthead Member

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    My recently purchased 73 was a standard coupe from factory with open differential. Found and bought what I was told was a 73 z28 posi with 3:73 gears in excellent shape. Had a shop set up to swap em and mech said the z differential was 1 inch wider not to mention I was told by seller in excellent shape just need to drop in. Axles were bad. Did they make different width rear ends in 73? Could he have measured wrong? Maybe not a 73 z rear end? Mech said the posi and gears looked real good though and suggested I find someone to swap out posi and use everything else including axles out of my open rear end. Is this a good idea?? Don't want to dump more money int the rear that wont work.
     
  2. BonzoHansen

    BonzoHansen Administrator Lifetime Gold Member

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    TMK all 2nd gen rears are the same width. Are they both 8.5" 10 bolt rears?

    Check the sticky post in this sub forum, it has measurements for 1st and 2nd gen rears.
     
  3. xten

    xten Veteran Member

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    I put a 12 bolt from a 1970 in my 73 sport coupe. Only thing I had to do was have a driveshaft made, the yoke on the 12 bolt was 7/8" shorter. Mounting, width was the same.
     
  4. big gear head

    big gear head Veteran Member

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    All '70 to '81 Camaro and Firebird rear ends are 61 inches wide with 30 1/8 inch axles. If yours is wider then it came out of something else. Someone could have put Camaro spring perches on an Impala rear end and used it in your car.
     
  5. Ruthead

    Ruthead Member

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    Sorry I had it backwards. The supposedly 73 z28 rear end is 1 inch narrower. My research (after reading the stickey's) points to possibly a gen 1 but the numbers on the bell housing don't seem to match the info shown so don't know what I got. I've included the pics of bell housing numbers. Anybody know what this is??? 20210909_143737.jpg 20210909_143737.jpg 20210909_143748.jpg 20210909_143748.jpg
     
  6. BonzoHansen

    BonzoHansen Administrator Lifetime Gold Member

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    Is that a 10 bolt?

    3894859 appears to be an 8.2 rear. Which never came in a 73 z28

    I suspect you got screwed.
     
  7. big gear head

    big gear head Veteran Member

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    Picture of the back of the housing please, where the cover bolts on. The 1st gen Camaro rear end is 60 inches wide, but the spring perches have to be moved to use it in a 2nd gen.
     
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  8. MChamp

    MChamp Veteran Member

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    everything I can find is from a 1st gen camaro/nova.
     
  9. Gary S

    Gary S Administrator Lifetime Gold Member

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    I find the same thing. 3894859 is first Gen Camaro and early Nova 8.2 10 bolt.
     
  10. Ruthead

    Ruthead Member

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    It is a 10 bolt. Talked to a guy today that said the same thing. He can move the spring perches and it'd work fine or take the inards out and use my housing. any thoughts on which way would work better? mech said the posi all looked good. If it's a 8.2 posi can the inards even be switched to and 8.5 10 bolt?
     

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