3rd Gen / L98 Engine Tech 1982 - 1992 Engine Related

Best way to make 91 rearend into posi?

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Old Jan 6, 2003 | 04:08 AM
  #1  
Polo-94Z28's Avatar
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From: Wheaton, IL
Question Best way to make 91 rearend into posi?

Just picked up a project car (sig) whats the best way to get rid of the one wheel wonders. As I am having serious traction problems. I would Like to help on that a tad. Is it possible to make a 4th gen Z28 / T/A rear end fit? Is there any modification involved? Id rather not spend 2k on a moser or ford rearend.

Thanks

Laterz
Old Jan 6, 2003 | 06:24 AM
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Tobe2wild's Avatar
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From: Rock Hill, SC
The rear is the same as a 4th gen a 7.5 10 bolt. Im not sure what gears are in it but you can get this posi and buy a set of gears for around 250. This is a new takeout posi from a 4th gen.
http://www.slponline.com/view_produc...TNUMBER=64501T
Old Jan 6, 2003 | 08:47 AM
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From: Flint, MI
best way that i found was to buy the $100 dollar stock posi from slp and put that in as long as you have decent gears like 3:23 or higher (i had 3:42 when i did it) you already have the 28 spline axles stock. just buy a stock posi and swap out the open wheelie peelie. thats what i did in my 91 rs that had a 305 tbi that i switched to a 350 carb. its held up great. hope this helps.

later,
Nick J
Old Jan 6, 2003 | 08:55 AM
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The zexel torsen take-off Diff from SLP is definately the most affordable way to go. A lot of people prefer this type of differential over a conventional clutch-type because it won't ever wear out, and is strong enough to put up with as much abuse as most people will give it. I installed it in my IROC, which meant that I had to upgrade to 28 spline axles. I bought a nice set of Moser axles, and my total cost still wound up being around the same as what an Eaton posi would have cost, and I wound up with a stronger rear end. I haven't driven the car much since I added the posi, but so far I'm very happy with it.
Old Jan 6, 2003 | 08:55 AM
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From: Carleton, Michigan
You were on the right track with the 4th gen rear. Get you a 4th gen rear something with a v-8 preferably a manual trans, gear ratios should be between 3.42 and 3.73 Great gears to run with a 700R-4 You will have 31 Splined axles which are stronger and you will have an extra 1.5 inch of backspacing for wider rear tires.. This is a direct bolt in installation no different than your stock piece, except for the e-brake, for that you will need GM Part # 10164125 for the e-brakes to work..
Old Jan 6, 2003 | 01:38 PM
  #6  
Polo-94Z28's Avatar
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Mmm... you guys have been very helpful. Thanks alot, I will look into the SLP differential. Right now the gears are 3.07, brandnew, way better than the 2.72 or whatever was in it.

Once again thanks
Old Jan 7, 2003 | 07:31 AM
  #7  
Jim85IROC's Avatar
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A 4th gen rear doesn't use 31 spline axles. It uses 28 spline axles, which is why the Zexel diff will work in our cars.
Old Jan 7, 2003 | 11:38 PM
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Striker27's Avatar
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From: Detroit,MI,USA
Not to sound blunt but cant you just get a Power trax locker for that rear end?????
Old Jan 8, 2003 | 02:25 AM
  #9  
Black91Z28's Avatar
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From: Omaha, Ne, USA
where can u get a 4th gen rearend for fairly cheap?? I havent been able to find one on ebay
Old Jan 8, 2003 | 09:52 AM
  #10  
aklim's Avatar
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Auburn makes posis for this car in 26 or 28 spline axels.
Old Jan 8, 2003 | 01:13 PM
  #11  
Ucantcme57's Avatar
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From: Carleton, Michigan
I would Check the paper for people parting out cars, check the towing and or collision shops Junk yards.. I picked up my rear from a 30th aniversary Camaro, with a 3.42 Posi, Dual Piston PBR Aluminum Calipers, 11" Rotors.. I picked it up for $250.00 and it bolted right in.. I even got an adjustable PanHard bar off of it with the rear.. Some 4th gens had the adjustable bar..

Kevin
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