Rear differential gasket newer models

obbop · August 21, 2004

Found some discussions across the Web about how some rear differential cover gaskets are lacking needed openings that may result in bearing failure.

Not sure if this is true or not but it may be a good idea to be aware of the possibility.

Appears the "good" gasket, the one from GM has a part number of 26066456

Here is a pic from another site showing the good gasket atop the bad style lacking the cut-outs:

http://scican.net/%7Ejbpalmer/Impala/gmfel.jpg

A small amount of info is here... scroll down to view:

http://scican.net/~jbpalmer/Impala/

I am unsure of when changes were made in the GM axle requiring the newer gasket. One message board thread told of early bearing failures and a mechanic mentioned their shop had come across several of these failures and had reported it to GM but GM took no steps to inform the public about the need for the new-style gasket.

My info is sketchy and not backed by personal experience but felt this info should be passed along. It may have already been covered here but my on-site search did not find the discussion.

I visit several GM and Checy truck message boards but have not seen this topic posted at any of them. I will post it here only and, if you believe it should be spread around, feel free to post the info elsewhere.

Thanks!!!!

asepgrad98 · August 21, 2004

looks like an aftermarket gasket was poorly designed. This is mostly a non-issue for 99+ GM trucks due the drain plug allowing fluid changes with out molesting the gasket.

MS3DALE · August 21, 2004

This is mostly a non-issue for 99+ GM trucks due the drain plug allowing fluid changes with out molesting the gasket.

My '04 1500 does not have a drain plug and GM stopped putting them in sometime in either the 2000 or '01 model year,why I have no idea,probably cost reasons,all I know is that now its a pain in the butt to change the fluid compared with my '99 I had.

bigdogs · August 21, 2004

My 03 Sierra 2500HD has a drain plug at the bottom of the case.

commanche1 · August 21, 2004

i just changed my gasket on 1998.no drain plug. MAKE sure you have the right socket to take of the boltsf.dont use those ones with the many sides,use one with 5 side type.if you screw the bolt head up, oh my. those bolts on mine were rusted in badly.i put compound on them now to get out easier next time.they were very tough to remove.i bought a gm gasket for 3 dollars at chevy garage.there are 2 gaskets for that year too.1 is much bigger.take care

budhayes3 · August 21, 2004

Perfect timing for this thread!

The big brown truck showed up this week with my TA Performance aluminum rear differential cover/girdle. Hoping to find the time to install it soon. It came with it's own gasket, plus I have a GM gasket that I bought a little over a year and a half ago when I changed my diff fluid. My rear has drain and fill plugs, so I didn't use the gasket but hung on to it. I want to compare the gasket that came with the cover to the GM one (after I check the part# on it) and see how they differ. Unfortunately my GM one is in my mother's garage and not here or I'd check it right now.

MS3DALE · August 21, 2004

i just changed my gasket on 1998.no drain plug. there are 2 gaskets for that year too.1 is much bigger.take care

Yes,on some of the old body style 1500 trucks you could get a "Heavy Duty" chassis pkg. (RPO Code F44) that gave you a 9 1/2 inch rear end,11.15x2.75 rear brake shoes,bigger u-joints and an additional leaf spring (basically it was a light duty 2500 rear end)it increased the GVWR from 6200 lbs. to 6600 lbs.

That is where the different size gasket comes into place,my '94 and '97 had the F44 option and there was no gasket from the factory I had to use sealer.

And I forgot that the 2500HD's still have a drain plug!

tobypineo · March 12, 2006

I also have an '04 1500 without a drain plug. I can't see why that made sense to them. $$ I guess. Anyway, I have a 10 bolt rear and was just wondering if this part number 26066456 is the right one for my truck. Can someone please verify this?? Thank you.

MS3DALE · March 13, 2006

Yep,26066456 is what you want to use

Dave in Mpls · March 18, 2006

i just changed my gasket on 1998.no drain plug. there are 2 gaskets for that year too.1 is much bigger.take care

Yes,on some of the old body style 1500 trucks you could get a "Heavy Duty" chassis pkg. (RPO Code F44) that gave you a 9 1/2 inch rear end,11.15x2.75 rear brake shoes,bigger u-joints and an additional leaf spring (basically it was a light duty 2500 rear end)it increased the GVWR from 6200 lbs. to 6600 lbs.

That is where the different size gasket comes into place,my '94 and '97 had the F44 option and there was no gasket from the factory I had to use sealer.

And I forgot that the 2500HD's still have a drain plug!

<{POST_SNAPBACK}>

That's odd - After reading this thread I went and looked at the rear diferential on my '02 Suburban, as it's due for a fluid change. There appears to be a drain on the bottom of the differential (I'm assuming that's what the 3/8" square drive plug on the bottom is).

pm26 · March 18, 2006

This is mostly a non-issue for 99+ GM trucks due the drain plug allowing fluid changes with out molesting the gasket.

My '04 1500 does not have a drain plug and GM stopped putting them in sometime in either the 2000 or '01 model year,why I have no idea,probably cost reasons,all I know is that now its a pain in the butt to change the fluid compared with my '99 I had.

<{POST_SNAPBACK}>

No differential drain plug on my '06 Z71 either

Just how much money do these people save by eliminating one drain plug? My '95 Nissan turck had a fill and drain plug on both differentials, on the manual transmission, and the transfer case.

tanked_darren · September 3, 2010

Turning and cornering can cause a vehicle to turn over. Vehicles remain stable because of the use of differential. All vehicles should have this.

tanked_darren · September 3, 2010

Whats wrong with good ol' silicone?

Z45 · September 3, 2010

The presence or the lack of a rear drain plug is due to who manufactured the housing and what assembly plant built the truck. I have never seen a drain plug in my last 5 trucks that were all built in Oshawa Canada. Not all the rear's are cast in the same place. A few years back when AAM when on strike in Mich, plants in other countries were sourced. I recall a service message that explained certain oddities from the one made in France.

Fwiw - My 2010 has the fill plug on the rear cover.

You should always use a gasket on the rear cover. They are designed to seal with a gasket. Problems with silicone or RTV seal is they often leak due to improper use. The product needs to cure a certain amount before installing cover and then before installing lubricant. Also some synthetic lubricants can cause a chemical reaction with the sealer so you need to buy the correct stuff. Also, it may not start to leak right away but gradually over time.

Put on the gasket, if done right, its fool proof and you fill the lube and drive it right away.