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Seeking 7.5” 10 Bolt Advice...

Discussion in 'Differential & Driveline' started by 1987 GMC Jimmy, Aug 10, 2020.

  1. 1987 GMC Jimmy

    1987 GMC Jimmy Automobile Hoarder

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    At almost 300K miles, the Corp. 10 in my car is singing its swan song. I’m going to try and make it a little longer, but it’s time to start planning what I’m going to do after. Ideally, I’d just keep the current axle since it has the control arm ears and the spring perches. As it stands, it’s a 2.56 ratio, 28 spline (I think) and open. The ratio doesn’t bother me as much because it has good highway manners, but the lack of positraction sucks. In a perfect world, I’d get a 9C1 8.5” that already has 3.23 gears and the Eaton G80. Not the gold standard in limited slip but okay for what I do/need. People want too much for the whole setup, and they don’t seem to be very available.

    Realistically, it seems like I’ll have to get a MotiveGear master kit for the 7.5”, $260, a posi setup, expensive, and then send it all to the builder. I’ll be $6-700 in the whole before labor, which seems unreal to me. If anyone can recommend a good posi unit, aside from Eaton, for the 7.5”, I would appreciate it. I’ve seen several brands that ring a bell, but I don’t know their quality. Also, if anyone has any suggestions or leads on a compatible 8.5” or even a 12 Bolt, I’m open to any input. I’m assuming a 12 would be from an old Bel Air, Biscayne, Caprice, etc., and then my only options on the 8.5” are a 9C1 Caprice or a hot G Body. Maybe an F Body?

    I’m better than I used to be, but I don’t pretend to be an expert on these enigmatic pumpkins.
     
  2. The88

    The88 What's broken this time?

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    Check with Quick Performance. They have good prices and the guys there are knowledgeable. I have bought from them a couple times.

    I know a gear guy that shouldn't be that steep for install to your west. If you were interested.
     
  3. The88

    The88 What's broken this time?

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    double post
     
  4. 1987 GMC Jimmy

    1987 GMC Jimmy Automobile Hoarder

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    I’ll look them up when I get home, and I’ll take any references, too. Feel free to share here, or if you wanna PM me, that works.
     
  5. The88

    The88 What's broken this time?

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  6. bucket

    bucket Super Moderator Staff Member

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    I didn't realize they even put a 7.5 in some B-body cars.

    Is the 5x4.75 bolt pattern a must? And if so, are you willing to have 5x5 axle redrilled for 4.75?
     
  7. Curt

    Curt Full Access Member

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    I think you should try to rebuild the unit yourself.A few tools from Harbor Freight.There’s a massive amount of knowledge on YouTube.I rebuilt my first axle a few months ago.I wish I could say it was all peachy,but there was a few hiccups.However,determination and help from the internet put me over the line.
     
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  8. Curt

    Curt Full Access Member

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    By the way,Eaton is an amazing company with amazing products.It’s a safe bet.
     
  9. The88

    The88 What's broken this time?

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  10. 1987 GMC Jimmy

    1987 GMC Jimmy Automobile Hoarder

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    Sorry for the belated response. You thought they came with 8.5s or... So what you’re saying is my current wheels are a no-go if I went from 7.5 to 8.5 unless I redrilled?
     
  11. CorvairGeek

    CorvairGeek Full Access Member

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    7.5 axles are all 4.75 pattern while 8.5s were available in both, IIRC.
     
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  12. Rusty Nail

    Rusty Nail Whatever!

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    That sounds right CGeek and I also want to agree with Curt.

    My first thought involved not spending one dime in a 7.5...
    F body axles are too narrow I bet.

    Your pretty good with the wrenches man...why don't you do it yourself? Screw spendin all that money right now!
    Besides when you'ree finished you could tell the rest of us how. :D
    Might even learn somthin.

    AND THEN ?

    and then think of all the possibilities. ;)
     
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