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Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Transmission - Rearend> 1983 Z28 rearend problems?
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Topic Review (Newest First)
07-07-2013 08:14 AM
Tom' Did have one on door before paint gone now do have plate on radiator support. Will have to tell my wife goverment passed a bill for 85 and older cars must have rearends updated lol
07-07-2013 07:58 AM
big gear head The codes are on a white sticker that is usually on the bottom of the console lid or on the back of the spare tire cover. Yours might be in a different location. If you can find it you will have all of the information about what your car came with, including the engine, transmission, suspension, brakes and other options. The codes are in alphabetical order and the rear end codes start with a G, the engine codes start with a L and the transmission codes start with a M.

Tom's Differentials is a great place to get Eaton parts, installation kits and AAM axles. His prices are good and his parts are among the best. He is kind of a grumpy old fella, so don't take it personal if he isn't cheerful.
07-07-2013 07:48 AM
Tom' More street than anything i guess the eaton posi ,couldn't find any numbers spare cover or console who's the suppliers
07-07-2013 07:27 AM
big gear head You have 2 weak links in the drive train, but as long as you don't abuse it too much it should be fine with street tires. The T5 and the 7.5 rear end can not handle a lot of abuse.

If this car will be built toward street/strip use then the Eaton Posi or Yukon Dura Grip would be a good choice. If it will be built more for street and auto cross/road racing then the Truetrac or Torsen would be a good choice. All of these are available in 3 series with 28 splines. When you make your choice I can recommend a good supplier for the parts.
07-07-2013 06:24 AM
Tom' Motor has about 330hp just put a world class t5 in .not going to race it but want to do it right without going over board ,is this enough info for a suggestion of what I should get 28 spline definitely. Thanks
07-06-2013 07:34 PM
Tom' Are these manuals known to wrong. Will check spare cover
07-06-2013 05:22 PM
big gear head If it's an original 3.73 Auburn rear end then it will have RPO coded GT4 and G80 on the sticker on the bottom of the console lid or on the back of the spare tire cover.

Just looked at the pic and that is a standard differential. If you had an Auburn then it's gone now.

If you decide to put another differential in it I do NOT recommend using another Auburn. They are at the very bottom of my list of good differentials. I would recommend using a Eaton Posi, Eaton Truetrac or a Yukon Dura Grip, depending on what you want to do with the car. I would also recommend upgrading your 26 spline axles to the later 28 spline axles at the same time.
07-06-2013 05:00 PM
Tom' Thanks he's no longer in business. Good for him
07-06-2013 03:40 PM
lmsport Thats definitely a standard open diff.

I hate to see people get ripped off by mechanics.
07-06-2013 03:11 PM
Tom' I have pic on profile thanks again
07-06-2013 02:53 PM
Tom' All the numbers match up with 3:73 vin 5jq is the axle code hayn
es manual says 3:73 posi
07-06-2013 02:50 PM
lmsport I dont think it came from GM with a 3.73.
07-06-2013 02:22 PM
Tom' Car came with 3:73 went back with same will post pic I really appreciate the responses guys
07-06-2013 12:42 PM
big gear head Can you post a pic?

The '83 would have had the Auburn limited slip differential. When they wear out they stop spinning both tires and at this point they are scrap metal. You can not rebuild them.

Here is something to think about. The 7.5 rear end uses a 2 series differential for 2.14 to 3.08 gears and a 3 series differential for 3.23 to 4.56 gears. If you had a 2 series Auburn and you went to gears in the 3.23 to 4.56 range then the guy who put the gears in might have swapped your 2 series Auburn for a 3 series standard differential so that the gears would fit.
07-06-2013 11:29 AM
Tom' I did no springs tried to get numbers on carrier can't see any think I was dupped went to auburns web site didn't look the same
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