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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!

    GM 7.5 & 8.5 10 bolt common problem

    GM B-Body Forum

    Posts : 743
    Join date : 2013-01-14
    Age : 26
    Location : Flint/Detroit, MI - Charlotte, NC

    GM 7.5 & 8.5 10 bolt common problem

    Post  GM B-Body Forum on Mon Jan 20, 2014 7:31 pm

    A common problem with the 7.5s and also the 8.5s is the pinion shaft lock bolt. The bolt wears down then eventually shears off. Once that happens the cross pin is free to do what it wants, it hits the pinion gear every revolution carving deep grooves and leaving huge chunks of metal in the oil to be circulated by the ring and pinion. This is what i experienced. I opened the cover and the oil was silver, from all the metal shavings. My cross pin is so badly damaged i cant get it out, and the pinion shaft bolt sheared and is stuck in the carrier, and the carrier is bent up from the cross pin. Theoretically its a quick fix but in my case, my rear end is fried. You can see in the pics below what kind of damage it did.

    Last edited by GM B-Body Forum on Mon Mar 10, 2014 11:00 pm; edited 2 times in total

    1979 Caprice Sport Coupe, 400hp Vortec 350, Th350, GM 8.5 w/disc brakes, 3.90 gears Detroit Truetrac, 2.5" stainless duals w/ x-pipe, Dynomax race bullets.
    1984 Caprice Sedan, 305 motor, 700r4
    1978 Caprice Sedan, 305 motor, th350
    1993 L99 Caprice, 4.3 v8, 4l60 trans
    1972 Ford F-100, 302 windsor, c4 trans
    2001 BMW E46 330i, 3.0L

      Current date/time is Mon Jan 21, 2019 11:59 pm