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12-bolt rear end

Discussion in 'Chevy Trucks' started by whwright, Aug 7, 2003.

  1. whwright

    whwright Member
    Messages: 39

    I have a 1983 Chevy "parts truck" that I'm scrapping. It's a C-10 Silverado that had a 305 and 3-speed auto. Somewhere along the way, someone put 3/4 ton rear leafs on it. Right now it has no engine or transmission. Surprisingly enough, it has a 12-bolt rear end in it (it has 12 bolts in the cover, anyway). I'm wondering if it's limited slip or not.

    If possible, I would like to avoid pulling the cover (in other words, I would like to avoid the mess).

    So...two questions.

    1. Did Chevy put "non-posi" 12-bolts in the 1/2 or 3/4 ton trucks in or around 1983?

    2. There's no transmission, so the pinion yoke (correct term?) is just hanging out there. If I jack up one wheel and leave the other on the ground, will I be able to tell if it's a limited slip?

    Thanks.

    Wayne.
     
  2. wyldman

    wyldman Member
    Messages: 3,265

    Most of them were non-posi.Jack up one wheel and see if you can turn it (the other wheel must be on the ground).If you can't,than it's a posi.If you can,it's an open diff.

    It is also possible you have a gear type bias unit,which only kicks in when there is a wheel speed difference.Not quite sure on how to test for that one,probably just open the cover and see.
     
  3. whwright

    whwright Member
    Messages: 39

    Thanks for the info, Wyldman.

    If it's not a posi, would it be worth the trouble of salvaging it before I scrap the truck?
     
  4. wyldman

    wyldman Member
    Messages: 3,265

    Wouldn't hurt,as the 12 bolts are getting much harder to find.It will also fit your 86 as well.

    It must not be the original rear from that 83,as it should of had a 10 bolt in it.
     
  5. whwright

    whwright Member
    Messages: 39

    Thanks Wyldman. You are a plethora of valuable information.

    I've never had a 12-bolt before! Can I make it fit my '75 Grand Prix?

    Off topic: your idea for "fixing" the temperature gauge worked perfectly.

    Wayne.
     
  6. wyldman

    wyldman Member
    Messages: 3,265

    Glad to hear the temp gauge works good :D

    The 12 bolt would not fit your Grand Prix,at least not a direct bolt in.The truck rears are wider,usually 62" or so from drum to drum,so it would have to be narrowed.Most GM car rears were only 54-58" wide.I think the Grand Prix would also have coils,and control arms,so you would need to do a bit of welding for the spring seats and control arm mounts.If it does have coils,it would probably be easier to just find the right 12 bolt for the Grand Prix.

    I would still keep the 12 bolt out of the truck though.You could sell it and make a few bucks.