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GM B-Body Forum, 77-79 Caprice/Impala Forum

A forum for all the owners and enthusiasts of General Motors B-Bodies from 1965-1996, but dedicated to the owners of 1977-1979 Impalas and Caprices. Join up now!


    8.5 rear swap into my 84??

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    johncaprice
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    Posts : 3
    Join date : 2016-07-22

    8.5 rear swap into my 84??

    Post  johncaprice on Sat Jul 23, 2016 12:07 am

    Hey everyone,
    New member here. Just picked up a 84 Caprice 2 dr.
    Car has a wicked 406 sbc/TH350 combo; as you can see the rear diff is the weak link in the driveline.
    It has the stock 7.5' open rear in it now;
    I want to install a built 8.5" (beefy posi unit, bigger axles, gears, etc)
    Now, i have heard that the disc brake, posi rears out of the 94-96 Impala SS will bolt right in.
    However, I have found these rears to not be as plentiful as i first thought
    (they are scarce honestly, supposedly all the circle track guys ate them up already)
    Id love to bolt a 3:73 disc brake posi (from a Brougham, apparently) into this car and be done with it  after a little rebuild and new brake prop valve. But i just can't find a complete unit available near me. Ive got a pretty good network of parts sources and I've exhausted all if them (8 junkyards, eBay, craigslist, racejunk,and a lot of 'chevy-friends')
    Now my question is; does anyone know where i can find just a REAR DIFF HOUSING for a mid 90's Impala SS;
    then i can build it how i like?
    Casting/Part #'s?
    Parts sources?

    Any info anyone can give me would me greatly appreciated. THANKS guys!!!
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    terry cronk
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    Posts : 165
    Join date : 2015-08-19
    Age : 70
    Location : Mid-Michigan

    Re: 8.5 rear swap into my 84??

    Post  terry cronk on Sat Jul 23, 2016 9:57 am

    Check out "Bill" Elvis article in "share with us" forum.
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    terry cronk
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    Posts : 165
    Join date : 2015-08-19
    Age : 70
    Location : Mid-Michigan

    Re: 8.5 rear swap into my 84??

    Post  terry cronk on Sat Jul 23, 2016 10:20 am


    Axle Ratio RPO Code Ring/Pinion Teeth Application
    2.56 GM8 41/16 Std. Roadmaster LT1
    2.73 GU2 41/15 Std. Caprice L99 (exc. 9C1)
    2.93 GW9/GU3 41/14 Std. Caprice LT1 (exc. 9C1), Opt. Roadmaster LT1
    3.08 GU4 40/13 Std. Caprice 9C1/LT1 (Police), Std. Impala SS
    3.23 GU5 42/13 Opt. Caprice L99, Std. Caprice 9C1/L99 (Police)
    3.42 GU6 41/12 Std. 91-93 Caprice 9C1/L05, Std. 94+ Fleetwood w/V4P
    3.73 GT4 41/11 Std. 91-92 Fleetwood Brougham w/V4P

    *V4P = 7,000 lb. trailer towing package... look for a hitch
    .

    From Seventy nine.


    1977-1996.

      Current date/time is Sat Jul 22, 2017 8:47 am