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Discussion Starter · #1 ·
Want to add new fluid to the differential. How to add fluid?
 

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If your looking at the back of your car on the passanger side you will find a 3/8 square bolt to the front of the rearend all you do is take a ratchet no socket and take the bolt out fill it tell it starts to run out put bolt back in and and your done as far as filling it.. if your going to change the fluid then you have to take rearend cover off get a gasket from autozone and some ornge rtv clean cover and rearend really good with brake cleaner put rtv on rearend and cover put gasket on cover side put cover back on tork to specs let rtv dry a couple hours, i let mine dry overnight fill and your done make sure you put the right rearend fluid in and if your car has posi you need an aditive that you put in first before the gear oil comes in a little tube ask some on at your local parts store hope this helps
 

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And as far as the additive for the posi, your better off getting that from a dealer. I had seen posts before the crash that other brand additives make the rearend make more noise than GM additive.
 

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And as far as the additive for the posi, your better off getting that from a dealer. I had seen posts before the crash that other brand additives make the rearend make more noise than GM additive.
bought it yesterday. 12.00
 

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...everything that was said already, but you do not need to use rtv when putting on the fresh gasket. I have done this to 2 cars without using rtv, and all has been good.

Also be sure to use the correct gasket with the "holes".

I believe this is the correct one, but you should cross check that part number just in case as I am going off memory on that one:
http://rmsautoparts.com/proddetail.php?prod=RDS55028-1
 

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Is it true GM built the rear ends w/ the incorrest gaskets? Where are the extra "holes" if so?
 

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At some point they started selling gaskets without the small slits in the middle. When you take down the the cover you see that they are covering two larger holes. The cover is molded to allow fluid to flow to these holes. Going without the holes will not kill your rear end right away, but if you don't do too many turns (like Highway Patrol) you will have under-lubed rear axle and eventually it will fail.
 

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Several times I have also pulled the entire differential out of my cars, installed and changed fluids. I have never used any type of RTV on the housing cover, though I did coat both sides of the gasket with a thin coat of greese. This will hold the gasket in place so you can install the cover properly. Also helps if you ever have to take the cover off again. I purchased a real nice differential cover from Mike at Focus Tech that allows me to drain without taking the cover off.

Larry
 

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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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