Transmissions and Drivetrain Need help with your trans? Problems with your axle?

86 Firebird 10 bolt LSD or Posi?

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Old Jun 25, 2010 | 12:44 PM
  #1  
Driver59's Avatar
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Joined: Aug 2006
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From: Aviano AB, Italy
Car: 1986 Pontiac Firebird
Engine: Custom built 350
Transmission: 700R4
86 Firebird 10 bolt LSD or Posi?

I was wondering if my stock 10 bolt rear is a LSD or a actual posi. Right now I have the wonderful "one-wheel peel" that I'm trying to cure.

I was wondering if I can rebuild the diff, with new clutches or if I need to swap to a true posi diff.

Thanks for the info guys
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Old Jun 25, 2010 | 12:55 PM
  #2  
89_RS's Avatar
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Joined: Jul 2008
Posts: 808
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From: Ft Wayne, IN
Car: 2003 F-150
Engine: 4.6L Modular V8
Transmission: 4R70W
Axle/Gears: Ford 8.8"/3.55 LSD
Re: 86 Firebird 10 bolt LSD or Posi?

Originally Posted by Driver59
I was wondering if my stock 10 bolt rear is a LSD or a actual posi. Right now I have the wonderful "one-wheel peel" that I'm trying to cure.

I was wondering if I can rebuild the diff, with new clutches or if I need to swap to a true posi diff.

Thanks for the info guys
A stock 10-bolt is an open differential that has 2.73:1 gears. That one-tire-fire you're getting is because the differential is open, meaning that the wheel that slips gets all the power. You would have to buy an LSD differential carrier, possibly new gears, and even new axles depending on the splines the carrier is designed for to cure that one-tire-fire.

It won't be as simple as opening the diff and replacing a few parts. This would almost be a major rear end rebuild. This is a list of a few of the LSD style carriers avaliable for a 10-bolt. Also in that list are a few lockers. They perform like a locked diff under acceleration, but open up during turning to allow for differentiation.

http://www.summitracing.com/search/Department/Drivetrain/Section/Differential-Rear-End-Components/Part-Type/Differential-Carriers/Axle-Model/GM-7-625-in/Stock-Case-Style/Open-case/Make/CHEVROLET/?Ns=Rank|Asc

Also, this tech article has some great info about how to rebuild your 10-bolt: https://www.thirdgen.org/beefinguprear

If you decide not to rebuild the 10-bolt and just swap out the rear end completely, the cheapest route is to get a Strange Dana S60 rear from Spohn. You would need a new driveshaft and brakes for it fit your car and possibly even a torque arm.

http://www.spohn.net/shop/1982-1992-...-Complete.html

Last edited by 89_RS; Jun 25, 2010 at 12:59 PM.
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Old Jun 25, 2010 | 02:12 PM
  #3  
big gear head's Avatar
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Re: 86 Firebird 10 bolt LSD or Posi?

LSD and Posi are the same thing. Posi is Eaton's brand name for their LSD that was used in the Chevy cars of the '60s and early '70s. The rear end in your car could have a standard differential or a LSD, depending on how it was ordered. To install a LSD read this. http://www.nastyz28.com/forum/showthread.php?t=19773
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