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rear axle differential fluid change

28K views 8 replies 8 participants last post by  B-Body Builder 
Is it true GM built the rear ends w/ the incorrest gaskets? Where are the extra "holes" if so?
Bill (Navy Lifer) gives you all the info you need on this subject here:
http://www.impalassforum.com/vBulletin/showthread.php?t=232216&highlight=gasket

By now, most of these rear ends could of had the rear dif gasket fix, but if your changing the dif fluid and GM additive......Here's the writeup on it from the Impala FAQ and how to tell?

http://www.raiden1.com/ss_faq.htm

If you look at the rear differential cover, you will notice two small indentations on either side directly in line with the axle tubes. These indentations are to direct the flow of oil through two holes in the differential case which then flows down the axle tubes to lubricate the axles and the outer axle bearings. The differential cover gasket is also supposed to have two holes in it, which line up with the holes in the case as well as the indentations to allow oil to flow down the axle tubes.

Starting in the 1990 model year, GM has been improperly installing differential cover gaskets THAT DO NOT HAVE THE LUBRICATING HOLES!! If you do not change this gasket to one that has the proper holes, your outer axle bearings, as well as the axles themselves, could be damaged by around 70K miles. The damaged (under lubricated) bearings potentially may wear grooves in the axle shafts, requiring that they also be replaced. If this is left unchecked, the metal bits from the damaged outer bearings and axles will also damage the inner bearings,
pinion bearings, as well as cause the spider gears to wear into the differential carrier.

All Caprice/Impala SS vehicles produced in 94, 95, and still in 96 (As well as 90-94 B-cars) have the improper gasket. The proper gasket is:

Fel-Pro: RDS 55028-1 (Autozone or Advanced auto parts etc..)
GM dealer Part # 15807693

The pic below shows the 2 lubrication holes at 9 oclock and 3 oclock on the rear end, and the holes being partially covered by the factory gasket. The 2nd generation GM design gasket fixed this, and so does the Felpro gasket.

 
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