How to know what kind of rearend I will need for my 1991 chevy silverado - Hot Rod Forum : Hotrodders Bulletin Board
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Old 12-15-2013, 06:56 PM
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How to know what kind of rearend I will need for my 1991 chevy silverado

Well a new project has swooped in for this christmas break, instead of starting the rebuilding process of my 400 small block, I will now be replacing my rearend in my 1991 silverado. I was wondering what information you all had on the ratio it may have. Another thing I was wondering was has any one put a limited slip (posi Track) in there truck? If so I was wondering what is a good kind to go with. I was also wondering if anyone had any advice on how to calculate the ratio so if I end up going to a junk yard I would like to be able to calculate what ratio in it and be able to know if it has a positrack in it or not? Thank you in advanced to all the much needed advice that you all have and may everyone have a Merry Christmas!!

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Old 12-15-2013, 07:01 PM
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Also, my truck is a 1/2 two wheel drive with a stock 350 V8 if that changes the type of rearend it would possibly have
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Old 12-15-2013, 07:54 PM
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Is it a ten bolt cover or a 14 bolt cover..that makes a bit of difference..Could be a 3.08 a 3.42 or a 3.73.. some of those were 4.10 ratio.. Posi or a locker would be a good investment on one of those trucks if you do not already have one..

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Old 12-15-2013, 07:56 PM
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Old 12-15-2013, 08:24 PM
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Originally Posted by OneMoreTime View Post
Is it a ten bolt cover or a 14 bolt cover..that makes a bit of difference..Could be a 3.08 a 3.42 or a 3.73.. some of those were 4.10 ratio.. Posi or a locker would be a good investment on one of those trucks if you do not already have one..

Sam
It's a 10 bolt rear end, and is a locking differential easy to install?
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Old 12-15-2013, 08:52 PM
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You have the 8.5 10 bolt with 30 spline axles. There is a white sticker in the glove box with a bunch of codes on it. The codes that start with a G are the rear end codes. The gear ratios go like this, GT4=3.73, GU6=3.42, GU5=3.23, GU4=3.08, GU3=2.73. The Eaton Governor Lock was the only limited slip differential offered in these trucks. The code for this is G80.

The Gov Lock isn't a very good differential. I recommend the Eaton Posi or Yukon Dura Grip for a replacement. Here is how you install it. http://www.nastyz28.com/forum/showthread.php?t=19773
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