My diff cover is leaking as it appears the lip has curled slightly at the bottom. Is there a method to fix this, or is this thing doomed to leak forever? The 9-bolt covers are near impossible to find. It's a BW 7.75 9-bolt with 3.45 gears, so I'd like to keep it in there. Any help or leads appreciated.

Kevin

 

Use the tubular style gasket. Seals them up every time no matter how munged the cover is, as long as it's not cracked.

 

Just use the goo, or do I use the paper gasket also?

Kevin

 

Skip the paper. It adds nothing functionally.

 

On my car, I always use paper and the goo, but I'm paranoid.

When you have the cover off, clean it off and do your best to straighten it out.

 

Thanks for the replies. I don't think it is bent too bad. I think somebody tried to get both wheels off the ground at the same time and used the differential as a jacking point. It had a very slow leak (almost like sweating) when I first got the car, until I decided to do a fluid change. Now I can't get it to stop (it's a very slow leak).

The first time I used a little hi-tack to hold the gasket to the cover. I figured the leak was the gear oil eating through the hi-tack. I just tried it again using only the paper and no permatex. It's still leaking slowly. This time I'll just use the permatex. I've never done it this way, but it seems as though it will be easier to get the Permatex on the cover and then bolt it to the carrier. Is this the preferred method, or will the seal be better if I make the gasket on the carrier? I really don't want to have to do this again.

Kevin

 

I don't think it matters too much which one you put it on; probably easier to put it on the cover though. I'd clean both surfaces up with lacquer thinner, smear a thin smear on both, lay a small bead like maybe 1/8" diameter around the cover with it going to the inside of the bolt holes, and tighten the bolts to around 18 ft-lbs or so (medium gentle pull with a typical 10" long 3/8" ratchet)

 

I also have a 9 bolt, mine doesn't leak. Here's what I do. Pull off the cover and drain out all the oil. Clean the crap outta the cover, both sides. Get it as clean as you can, scrape off ALL remnants of old gasket and goop. Clean up the bolts, get all the crap off them. Push the rubber plug out from the inside so you don't damage it. If it's still soft and pliable, clean it and reuse it. If it's gotten hard, go to GM and order a replacement, I just got one from the local Poncho dealer. Fix any dents or sharp ridges and gouges in the cover that you can. Be sure to clean out the fill hole until it's spotless. By now, the oil should have finished draining outta the punkin. Go up in there with your hand, under the carrier, and scrape out as much of the old oil as you can that is still in the bottom of the punkin casting. Clean the crap outta the mating surface on the punkin. Scrape off all traces of old gasket and goop. Wipe all oil off the surface.

Now lay the cover on your workbench with the mating surface up. Splooge some of the black goop on the cover's mating surface, and spread it around with your finger to get a uniform film around the sircumference, about 1/16 thick. Then take the gasket and lay it on the cover, line up the bolt holes and press it down. The goop will act as a glue to hold it down. Press the gasket down uniformly all the way around. Now splooge more goop on the gasket, and spread it around with your finger. Again, get a uniform film all the way around, about 1/16 thick. Now carefully take the cover under the car, slip it up and over the sway bar and position it on the *** end of the punkin and put in a couple bolts to hold it. Now put in the rest of the bolts and uniformly tighten them snugly.

Once the cover is on and all 9 bolts tightened, refill the diff with fresh GL5 80W-90 or 75W-90 oil. If you're running normal dino oil, also put in some Limited Slip additive. If you're running Redline or Royal Purple synthetic, no additive is needed. I use a little hand pump with a hose to pump the oil out of the bottle and up into the diff fill hole, you can get the little pump cheap at a parts store. Fill the thing until oil starts running back out of the fill hole. Now take the rubber plug and put some grease on the nose and neck. Push it up into the hole all the way, the heavy grease will help it go in smoothly and help seal it.

Recheck the tightness of the 9 bolts after a couple days. It should not leak any more.

When the cover is off, be sure to eyeball the ring gear for any signs of distress.

 

I know I'm a moron; but I don't see an advantage of 2 1/16" thick beads of silicone with a $5 piece of paper that's hard to get, over 1 1/8" bead of silicone with no paper @ $0 that's effortless.

Cleaning, wiping, filling and all that, is good.

Use lacquer thinner when you wipe your rear end. Well, the one in the car, anyway.

 

The gasket is not "hard" to get. It just takes one day. Any parts store can order it and have it for you the next day. Ever heard of planning ahead? Get the gasket in before you intend to start the work, or do what I do, and keep one as a spare, so you always have one at hand.

The part that's hard to get is the rubber fill plug. That takes a couple days from the GM dealer. I have a spare one of those as well.

The extea "thickness" that the gasket provides helpswith any surface irregularities in the cover or punkin. YMMV, if you want to use goop only, that's your biz. I'll stick with goop + gasket. Whatever floats your boat.

 

RB knows what he's talking about. The gaskets are getting harder to find. I went to 3 parts stores where they did not even have a listing for my car. They all said to use RTV. Even NAPA said to just use RTV!

On the other hand, the service manual says always use a paper gasket with sealer.

I have seen cars and trucks with leaking rears. They always have RTV all around. It makes me paranoid, but I'll bet it was more because they did a poor job cleaning and prepping.

I think either way should work.

 

I went into a local parts house, told the guy I needed a gasket for the 9-bolt, he looks it up on the computer and pulls the Felpro part number. On order. Simple. I can also get them at the local Kragen and the local Napa. I don't know what's the problem in your area, my local parts houses have no trouble getting the correct part.

I'm not saying he doesn't know what he's talking about, but that is not to say that I am "wrong" with wanting to use gasket plus goop. GM will tell you to use gasket + goop. Do as you wish, it's your car.