need help identifying a posi unit!!!!!!!

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speed_demon

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Ok I have this posi unit that a friend gave me for doing some work for him. It has 30 spline gears in it and 10 bolts that hold the ring gear but not sure if it will fit my rear end which is a 10 bolt . not sure if it is a stock unit or what here are some pictures

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crazy4offroad

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Looks like an old Eaton unit, but I cant tell what year/model axle it came out of.
 

speed_demon

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i'm going to assume that my rear end has 28 splines so if this will fit my housing i will need to get some 30 spline axles only difference i see between the 28 and 30 is that the 30 spline are a little bit longer.
not sure about bearing size though weather or not i'd have to install larger ones.

I found the numbers on my rear end (passenger side front of axle tube)
br3 g231

I have searched online and can't figure out what they mean.
 

crazy4offroad

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Mic the distance from the ring gear mounting surface to the short end of the unit, and compare it to yours. There could be a difference between carrier break numbers. I.E. 4.10-down carrier vs 4.56-up carrier.
 

speed_demon

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don't have a mic but can get one. The truck is just sittin' right now so i might just take the cover off and check it out when i get a chance.

BTW how much fluid should it take for my rear end?
 

crazy4offroad

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I would just get a couple quarts and fill it till it runs out the fill hole on the side. Shouldn't take more than 2 or 3.
 

speed_demon

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I would just get a couple quarts and fill it till it runs out the fill hole on the side. Shouldn't take more than 2 or 3.

cool Thanks!!! I got a gallon so I'm covered.
 

RetroC10Sport

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G231 will likely be July 23, 1981

The only refrence to BR3 I've found is a 1984-87 C10 10 bolt 2.73 non-locking; 8.5 ring gear; 11x2 brakes.
 

speed_demon

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G231 will likely be July 23, 1981

The only refrence to BR3 I've found is a 1984-87 C10 10 bolt 2.73 non-locking; 8.5 ring gear; 11x2 brakes.

SWEET thanks man that sounds about right. i'll know for sure when i tear it apart.
 

HotRodPC

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I agree with C4, that it looks like an older Eaton LSD unit. Not a locker for sure, and its not a GovLock. It looks alot like what 89S has in his Burb.

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speed_demon

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you know it really does look the same.
How does it perform?
I don't want a full spool cause this is my DD.
where can i get some 30 spline axles that would fit this unit?
and what has to be changed in order for this to work?

Thanks to ALL for taking the time to research and answer my questions.
 

HotRodPC

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Rather than go with 30 spline axles, it might be cheaper to replace the spider gears in the unit to 28 spline gears if that is what you have.
 

HotRodPC

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Its not a spool. I did some research. It is an Auburn Limited Slip Differential. They come in both OEM models and Aftermarket models. Yours is likley an OEM model and is the same as what 89S has in his Burb. The 30 spline unit is for 89 up 10 bolts, the 28 spline is for 71-88 models. Now, I don't know what years GM used them OEM. So if your truck is an 81, according to app charts is 28 spline and that unit is 30 spline you said. It also does appear the only differance is the sidegears in the unit. But, it might be just as easy to get axles out of an 89-91 Burb or Blazer. Should be the same length I'd think since both are Suqarebodies and the rear ends intechange. Hopefully that is enough info to get your going.

http://www.drivetrain.com/parts_catalog/positraction/auburn_positractions_lsd.html

http://www.pirate4x4.com/tech/billavista/PDFs/New Jun 2003/Auburn spools and mini-spools.pdf
 

HotRodPC

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