74 Z28 posi unit

Discussion in '1974 Specific' started by CamaroNmotion, Jan 23, 2021.

  1. CamaroNmotion

    CamaroNmotion Veteran Member

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    Question for anyone who has gotten inside their rear axle posi unit. Since GM used 2 different types of posi units, what type was found in their Z28? Was it the Eaton which used clutch plates OR the Chevy unit which used clutch cones?
     
  2. Gary S

    Gary S Administrator Lifetime Gold Member

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    It most likely is neither of the ones you listed. The Eaton was used on the 12 bolt. Starting in 1971, all Camaros got the corporate 10 bolt which usually has the traction lock which is a clutch type posi similar to the Eaton. The Eaton used 4 coil springs to preload it while the Traction Lock used a S shaped spring to do the job.

    The cone type posi was used in the 60s on Warner posi on some Chevys, and later on the Auburn aftermarket posi.

    Just pull your cover and take a look. You can see what is in there. If you haven't seen it, it probably needs a lube change anyway.
     
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  3. CorkyE

    CorkyE Veteran Member Lifetime Gold Member

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    Gary, sometimes you are so insightful. :)
     
  4. boltupal

    boltupal Veteran Member

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    Gary is right , its most likely at 8.5 ten bolt. They are good units strong cheap and plenty of parts around.
     
  5. CamaroNmotion

    CamaroNmotion Veteran Member

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    Found a 35mm photo of my fluid change many years ago on my factory stock 10 bolt '74 Z28 rear axle. Can clearly see the "S" shape spring in place. Puzzle solved, thanks Gary.
    my 74 Z28 rear axle-posi unit.jpg
     
  6. zfool

    zfool Veteran Member

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    I’ve got several pics at home of the gears and numbers on 3:73. If I remember I’ll post them. Busy as all heck.
     
  7. CamaroNmotion

    CamaroNmotion Veteran Member

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    Please share. Want to learn more. Mine is a 3.73.
     

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