Would this Posi work in my 73 Centurion?

Discussion in 'Got gears?' started by Roadmaster49, Feb 24, 2013.

  1. Roadmaster49

    Roadmaster49 Well-Known Member

  2. Mark Demko

    Mark Demko Well-Known Member

    I wouldnt believe the sellers description. Im not a rear end guru, but hes not describing that carrier correctly.
     
  3. stubnosebrock

    stubnosebrock Well-Known Member

    Thats quite a bit of money for a used posi. Do you know for sure what rear your car has?
     
  4. Smartin

    Smartin antiqueautomotiveservice.com Staff Member

    It's not big money if it's a real 9 3/8 3.42 set.
     
  5. stubnosebrock

    stubnosebrock Well-Known Member

    Problem is, it doesnt look like the pinion is there, only the ring by the sellers description.
     
  6. Smartin

    Smartin antiqueautomotiveservice.com Staff Member

    I see what you mean. Kind of worthless without the pinion!
     
  7. monzaz

    monzaz Jim

    Well I will let you in on some info. That is NOT a 71-76 more like a 77-85 8.75

    The biggest thing is it is NOT 3.41 gear set. NO SUCH BEAST. GM does not put ratios on the gear sets they put tooth count (so it would be 3 pinion teeth and 41 ring...??? NO DOUBT IT.) That is a month date code 3 the gear is a 41 -16 (2.56). Please look at the ring gear once more. I can also tell this because the carrier flange is WAY over to the left if it were 3.42 the flange would be more to the center.

    17-1 17-2 17-3 17-4 all carrier breaks but for 28 spline carriers c-clip All from 1977-1985 era. cadillac and wagons came with these 8.75 rears. (the casting 17- # Is a sure way to tell. 71-76 casting numbers were still 248 249 250.

    Call him up and ask for the axle spline and see what it was.

    The only way it could be 31 spline is if it was from a wagon. IT might, but should be c-clip type. It has been one of the first 17-4 units I have seen.

    NOW IF it is 31 spline you could use it in the 71-76 BUT your will need a custom spacer to use a steeper gear set. Jim

    I have included pictures of the series and also you can see the difference from the older 65-76 full size carrier to the 77-85 carrier flange thickness too. This is a case where they do not make them like they use to deal. :)
     

    Attached Files:

  8. Roadmaster49

    Roadmaster49 Well-Known Member

    monzaz

    Thanks for saving me a bunch of money.
     
  9. monzaz

    monzaz Jim

    I email him and it is 28 spline C-clip unit so it is from the 1977-1985 era. it is a terd. :( Jim
     

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