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Back in January, I drained my rear end, put a new Gasket on, put the GM post fluid in, and filled the differential up with fluid. Since then, the cover has been leaking. When I put the Gasket on, I used RTV on the cover, and the housing, as I was told to do. When I asked the same person about it leaking, he said I probably should've just put it on one side (can't remember if he said housing or cover). As a GM dealership tech, I have access to online service manuals for GM cars, and when going through the cover Gasket procedure (after the fact), it made no mention of using rtv.
So, my question is, where do you think I went wrong? Could it of been that I used rtv, or put it where I shouldn't of? I have everything I need to do the same job again, so I want to make sure I do it right this time.
This is what I do and have never had a leak and have done it many many many times.....
I clean the sealing surfaces with a green Scotch Brite.
Then I put mega black oem gasket maker on the differential. Then I put some on the differential cover.
I use a gasket also, some don't but I do. Put the gasket on the cover then put it on and bolt it up but ONLY tighten the bolts finger tight and let it set for a half hour then bolt it down. Good to go
Awesome, I'll try that. I wonder if I didn't let it sit for long enough last time, thank you. Should I hit the inside of the differential with some brake clean to clean it out a bit? That's something I skipped last time. I didn't see any metal shavings or damage to the gears, but I also developed a constant roaring noise last time I did this too. I know the rear end is probably on it's way out, but I don't have money for a new one or a rebuild at the moment, so I'm trying to preserve it the best I can, for now. I was told it could be the viscous clutches making noise?
These cars didn't originally come with any sealant for the diff cover. I've bought a couple of them brand new so I'm very sure that I was the first one to remove the cover. That's why you don't see a sealant requirement mentioned in the service documents.
I don't typically use any sealant on these, other than maybe a bit around the bolt holes which also helps to hold the gasket in place, just a GM gasket (one of mine came from the factory with a double gasket - not sure if this was a mistake, but it wasn't leaking at all.)
Good advice about the LSD additive mentioned above for the Auburn rear. But the OP wouldn't have that in a '99 Z28 if it's still the stock rear. '98 was the last year for Auburn unless you ordered the SLP Auburn on an SS car in '99+.
I tried 1 felpro gasket and the cover leaked, removed it and cleaned the surfaces again. Applied gasket maker on the cover and the housing, waited an hour and installed the cover with new felpro gasket and installed the bolts finger tight in a cross pattern. I waited 24 hours for the final torque and then filled the rear, hasn't leaked at all.
Thanks for all of the help, everyone. When you apply the Gasket maker or RTV, do you spread it around with your finger, or just apply it from the tube and leave it as is?
I will spread it on the diff with my finger than on the cover I lay a very light but solid bead around the hole thing going around both sides of the bolt holes then spread it even and thin with a card or finger
Thanks for all of the help, everyone. When you apply the Gasket maker or RTV, do you spread it around with your finger, or just apply it from the tube and leave it as is?
How clean is your finger? I use the tip to apply it and let the cover smear it out, the instructions are on the back of the package also.
Just got the Gasket today, I know tightening pattern has been mentioned in here, and I can't remember how I tightened it last time, but I feel like that could've been another issue. This time, I was planning on tightening it as you would a an intake manifold, where you start in the middle and work out. That should be fine, right?
I'm sorry, I feel like I'm making this more difficult than it needs to be, but I just want to make sure I do it right this time
Just got the Gasket today, I know tightening pattern has been mentioned in here, and I can't remember how I tightened it last time, but I feel like that could've been another issue. This time, I was planning on tightening it as you would a an intake manifold, where you start in the middle and work out. That should be fine, right?
I'm sorry, I feel like I'm making this more difficult than it needs to be, but I just want to make sure I do it right this time
Hey man, you're not the first to have sealing stumbles on that diff cover.
I usually go in a pattern kinda like a intake manifold
I never use a gasket on the diff cover anymore, because they most always seem to leak. (Seeps through the gasket) Just use permatex. Bolt it up and let it set for an hour before you add oil. That's if you really want to make sure, but not necessary. Have not had one leak since.
I never use a gasket on the diff cover anymore, because they most always seem to leak. (Seeps through the gasket) Just use permatex. Bolt it up and let it set for an hour before you add oil. That's if you really want to make sure, but not necessary. Have not had one leak since.
I should of been more specific, I'm just a lube tech, so I do oil and tires all day. I'm still learning.
I changed the fluid and gasket on Tuesday, and so far no leaks. Thank you everyone for your time and help
I have question for you:
I have been a truck tech for over 40 years and just changed the oil on my wife's 16 Enclave, how do you get the filters off without making a huge mess?
Don't let people get you down, your young and learning, not everyone is a internet expert. I tell all my new techs that the reason us old guys know so much is because we already screwed up that job and learned the right way when we fixed the screw up. Glad you got your leak fixed.
I smear rtv on the cover then push the gasket on and let it dry. Then smear wheel bearing grease on the differential side (so the gasket does not stick to the differential) and install the cover. This way you will be able to remove and re-install the cover many times with out replacing the gasket. If you have a leak, it could be due to the cover being bent.
I have been a truck tech for over 40 years and just changed the oil on my wife's 16 Enclave, how do you get the filters off without making a huge mess?
Don't let people get you down, your young and learning, not everyone is a internet expert. I tell all my new techs that the reason us old guys know so much is because we already screwed up that job and learned the right way when we fixed the screw up. Glad you got your leak fixed.
There really isn't a clean way to do it. We toss a floor pan under the front of the engine, remove and replace the filter, and spray it down. It's usually best to spray it from the bottom, though. It's rough on those motors.
And thanks, I understand where he was coming from, though. Just saying I was a "GM tech" is misleading, haha
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Differential Cover Gasket 
