Advice on Factory Limited Slip Differentials

ssn696

Living in the Past
Supporting Member
Jul 19, 2009
5,385
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Permanent Temporary
Posting here rather than on the Wanted/For Sale section, since I need some facts to tailor my request. I saved a factory 3.08 ring and pinion for a 7.5 from the trash...and am looking for a used limited slip to fit this gear set. I am not sure whether the stock one shifted offsets at 2.73 or 3.08. Auburn coners and Eaton TrueTracs split at 3.08.
 

64nailhead

Goat Herder
Supporting Member
Dec 1, 2014
4,965
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Upstate NY
3.08 is a series 2 for a 7.5
 
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79 USA 1

G-Body Guru
Sep 2, 2011
951
93
Cheektowaga, New York
2 series uses ratio's up to 3.08 and down gears unless a ring gear spacer is used or aftermarket "Thick Gears" for 3.23 and up.
3 series uses 3.23 and up gear ratio's.
Gm 7.5 and 7.625 ring and pinion sets fit the 7.5 housing.
A/G body 7.5/7.625's had 26 spline axles until 1988.
 
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Cauterize

Floater of Valves
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Feb 9, 2019
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Deathbridge
The early s10/15's had 26 spline axles and can be easily found with LSD's. I found mine in a 4x4 s10. I do believe the later S trucks were 28 spline.
 
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64nailhead

Goat Herder
Supporting Member
Dec 1, 2014
4,965
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Upstate NY
I went down this path some years back. An excellent option is a GM factory Torsen. Finding these in a 2 series is not that hard because to most people, the 2 series is not extremely desirable due to gear ratio. But if you want to stick with the 3.08 or numerically lower gear set they are readily available.

Here's one that I quickly found on Ebay :

Two issues that you have to be overcome. 1st, it requires 28 spline axles. You can drop $300 or so on a set of aftermarket axles, i.e. Moser Axle. Or you can use a set of 2wd S10 axles from most every S10 upto 2002-04 (IRC). The issue with the S10 axles is they are about 5/16" longer that creates the 2nd issue. I resolved that with 2 pieces of 5/16" flat stock that I cut, drilled, formed to match the factory axle housing flange trapezoid type shape. ou have to remove your brake assembly and stick your spacer between the axle housing flange and brake assembly.

It's relatively easy in design, but you will spend some time making the flanges by hand. A Bridgeport would make it much easier, but I don't own one of those haha.

Cauterize mentioned finding a factory posi from an '88 or older S10 that will allow you to utilize your axles. This is a very easy swap if you can find one in any series, 2 or 3. I tried doing that with no success. I could not find one in a local junkyard, hence the reason I went with the Torsen.


Good luck.


Edit : something that s noteworthy with a Torsen, if you intend to drive this ever, repeat ever, on ice or snow, then be advised that a Torsen will literally not move on ice - ask me how I know.
 
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