I have a 1996 z28 auto. I found out why my posi isnt working any why whenever i put it into drive or reverse, it makes a loud banging noise. I opened up the rear and and could see right away what was wrong. The carrier assemply had been damaged pretty bad by the pin that goes into it.(which is probably from the kid who had the car before me, because i know he abused the car pretty bad) but anyway. A new carrier assembly is a little over 500 bucks, and i found a used rear end for 300 bucks. the inside is in great shape and gears are pretty good. It is out of a 94 z28. The guys says it is geared 3.23 but i thought mine was 3.73? if the gears are the same should i just drop my whole rear end and put the new one in. or just take the carrier assembly out, and if theyre different, can i put my gears in the odl one?

 

Make sure you get a Torsen carrier; they do not have clutches like the carriers in the lt1 cars. You should not have any gear higher than 3.23s, if it is a stock rear for a auto; the m6 cars came with the highest gears which are 3.42s autos only came with 3.23 max. I would get a torsen carrier or a whole rear end from a LS1 fbody. I am currently looking for a low priced torsen carrier for my rear; the clutches in my carrier are burned out. Here is one I found http://cgi.ebay.com/ebaymotors/GM-7-...5fAccessories.
It is a little more than I want to pay for a used unit though.

 

Get the complete rear end. It would be a lot easier to swap out a complete rear than to replace the carrier and set up the ring and pinion.

 

The stock gears in all 4th Gen A4's (automatics) are either 2.73 (GU2) supplied with the base V8, or 3.23 (GU5) supplied with the "performance rear axle" option.

Swap the entire rear axle assembly. Its just about impossible to set up used gears, even for an experienced shop. Note that you must have a rear axle assembly with the correct number of ABS sensors. If you only have ABS, you need a single sensor (3-channel system) on the differential housing, If your car has ABS + ASR (aka TCS) you need a sensor on the end plate on each end of the axle housings (4-channel system).

Personally, I don't see any advantage to the Torsen. I've got a HD Eaton posi (clutch type) in my 12-bolt, and after 11 years, its still working fine.

 

Last comment is correct you should just go with a new rearend and id go with 3.23's or the same if you want either way for you lt-1 or ls1 guys you can go to hawksthirdgenparts.com and they sell used rearends for the f-body for only five hundred dollars and they guarantee the rearends they sell are low mileage and will work proudly. Also if you decide to get a rearend with the different ratio you will need to reprogram your computer for it. This is easy though.

 

You should be able to find a reliable take-off rear from a V8 4th Gen, locally, for $250-300. Not sure if they will work "proudly" though......