Rear diff cover size and gasket question

[mrwitty_1]

Looking for a replacement rear differential cover so when I do oil change I can replace the rusted cover. From searching the posts I understand that all I-6 SWB Envoys use the 8" differential. RockAuto list one cover that states : Cover for 8.6", 8.5" and 8.2" GM rear, I take it the 8.2" will be what is called a 8", however they list two gaskets, one for the 8" and one for the 8.625. my question is the covers the same but not the gasket or is this not the correct cover for the 8" ? Confused... would like to have the cover and gasket in hand before starting.

 

[gmcman]

You likely have a vent tube on the top of the diff, reason I state this is BEFORE you pull the rear cover, be sure you have already removed the fill plug, DO THIS FIRST!

The fill plugs can be a real PITA to remove if they haven't ever been removed. You would need to use the vent tube for a refill if you can't remove the fill plug....it's a slow process.

Not sure about the covers.

 

[mrwitty_1]

GREAT THINKING !
I wouldn't have thought of that ! Thank You

 

[triz]

Unless it's leaking I would look for that fill and drain plug as GMCman stated above. Hopefully yours has one.

 

[gmcman]

I believe all 02's have the drain plug, for the fill plug, I wouldn't even mess with a 3/8 extension.....get a dedicated square drive plug socket, clean out the plug and make sure the square drive is fully seated. Once you round off the fill plug it's time to bend over.

 

[AbsoluteZero]

Looking for a replacement rear differential cover so when I do oil change I can replace the rusted cover. From searching the posts I understand that all I-6 SWB Envoys use the 8" differential. RockAuto list one cover that states : Cover for 8.6", 8.5" and 8.2" GM rear, I take it the 8.2" will be what is called a 8", however they list two gaskets, one for the 8" and one for the 8.625. my question is the covers the same but not the gasket or is this not the correct cover for the 8" ? Confused... would like to have the cover and gasket in hand before starting.

I'll relay my experience. Like you I decided to have a new gasket on hand before draining the rear differential. I can tell you with first hand info the cheaper of the two did not work on my 03. On RA's site one is listed at $2.36, the other at $18.10. Ended up using the old gasket. Hasn't leaked in several years of usage.

 

[C-ya]

I'll relay my experience. Like you I decided to have a new gasket on hand before draining the rear differential. I can tell you with first hand info the cheaper of the two did not work on my 03. On RA's site one is listed at $2.36, the other at $18.10. Ended up using the old gasket. Hasn't leaked in several years of usage.

On my '05, the listed 8.625" gasket was not correct. I used black RTV. No leaks.

I'm not sure if anyone knows the real numbers for the diff cover gaskets.

 

[mrwitty_1]

The following are the GM part #'s. Price from GM is very reasonable, just going with original GM.

12479377 AXLE COVER
BRAVADA/ENVOY/TRAILBLAZER; 113 WHEELBASE

12479379 AXLE COVER
BRAVADA/ENVOY/TRAILBLAZER; 129 WHEELBASE

Thank you for all the input

 

[glfredrick]

I always use RTV and no gasket. Done tons of them that way.

Also, for those on the trails who might have to do a trail repair out in the middle of nowhere because of a broken axle, punctured cover, etc., capture the gear oil into some sort of container, then store it in a zip lock baggie. When it is time to reinstall the cover just plop in the entire zip lock baggie full of oil and slap the cover in place. The gears will rip open the bag and the oil will be inside. The bag remains do no harm and will just disolve in the oil after a while. Makes an otherwise difficult trail repair a LOT easier!

Also, tapping on the drain plug with a hammer first helps for removal.