gear oil and limited slip additive?

I am going to do a gear oil change on the wagon. I see that it takes the typical GM 80w90 GL5 gear oil, so I plan on getting regular oil from the parts store/Wally World. I am guessing it takes 2.5-3 quarts...

What additive do you guys like for the posi? And is there a preference on a diff cover gasket?

We haven't had a vehicle with a real clutch type posi in a long while...

If it's stock G80, it isn't a clutch type, it is an Auburn cone type. Put in one bottle of GM ltd slip additive, then fill until it starts to come out the hole. Use a new gasket with the side holes.

I only use GM additive in GM posi units. Get the blue Felpro gasket with the holes in the side for the diff cover.

You can use silicone gasket maker if you do not want to buy a gasket.

Silicone/RTV is the DEVIL. I use it on Intake manifolds and that's it.

jayoldschool wrote:

If it's stock G80, it isn't a clutch type, it is an Auburn cone type.  Put in one bottle of GM ltd slip additive, then fill until it starts to come out the hole.  Use a new gasket with the side holes.

The correct response lies above.

Thanks for the info guys.

I like using a proper gasket when possible, so I will pick one up. I looked an Advance Auto has the proper one with the extra holes in it. We will also pick up a bottle of the limited slip fluid from the local Chevy dealer.

While I had the fuel tank out and the car was in the air I did the gear oil change. The old gasket did not have the two extra holes in it! It looked original to the car. Thankfully there was only a gasket and no extra silicone on there and the cover was stuck on pretty good.
The old oil looked decent while draining and didn't have any extra smell to it, so that is good. I cleaned out the housing and the cover. There was a bit of funk in there, not really surprised by that as the car has been sitting for so long. I took a wire brush to the diff cover and then gave it a quick coat of black paint to cover the rust and pretty it up a bit. Then reinstalled the new gasket and cover and refilled with a bottle of additive and a few quarts of gear oil.
One more project/maintenance item checked off the list.