Rear Differential Cover Replacement
 

I hate to say it, but my diff has a leak and I have no idea for how long. I really hope I didn't kill it. The entire lower quarter of the cover is soaked, and there is a wet mark in my parking spot under it. Never noticed till now.

Anyone have tricks to doing this with it on jack stands? My father did this on his S10 and said it was easy, but it looks different. Mine has what looks like a rusty pipe in front of it. Will this get in my way or can I wiggle the cover out. Every single bolt looks like it has a nice coating of thick rust and dirt build up. How do I tell which cover I have, that auto store said there were two different sizes. Finally, is it safe to shoot PB Blaster on the bolts to loosen them up?

Before you do anything, first make sure you can remove the filler plug. The rusty pipe would be the stabilizer bar. Should be able to do the cover gasket with the stabilizer bar in place. To get the correct gasket take the old cover to the parts store with you. In Michigan, I would buy a new cover as it may be rusted out - they are pretty cheap. When you scrape the old gasket from the housing, make certain ALL of the old gasket is removed (not just what is convenient). Old rear end cover gaskets are notoriously difficult to scrape off. Yes, PB Blaster is fine.

I'll attempt to remove the filler plug today after work then. So what if that plug doesn't come out? Am I just SOL? Will I need a drip pan or will little to no oil come out?

Defiantly wasn't going to get used here when a new one is only $11 - $20.

Its just a 3/8s drive fill plug. Use a breaker bar for leverage. No oil will come out of it. The oil comes out when you remove the drain pan

If you can't get the original fill plug out, then you can get rear covers with fill plugs incorporated into them (but they are more expensive). Better to know how you will fill it up after repairs, at the beginning of this process. Yes you will need a drain pan when you remove the rear cover. A quart or so should come out. When scraping gaskets and rust, take care to not get stuff into the inside area (bearings and gears ya know!) - you can stuff shop rags in the top area and let them hang over the gears. Plan on taking your time and expending considerable effort scraping all the old gasket material off the rear housing sealing surface. If you eventually get the surfaces clean and oil free using carb cleaner, you can put a thin film of RTV sealer on both sides of the gasket to seal things up and then let sit overnight. But don't waste your time unless it is absolutely oil-free. RTV doesn't adhere in the presence of oil. Get ready to get greasy with some really smelly stuff!!!

The videos I saw doing this jammed a white rag into the diff when the cover was removed to prevent shavings from getting into the diff, I plan on doing that. I don't have carb cleaner laying around anywhere, but have been told brake cleaner (which I have plenty of) is good for almost anything could I use this instead to clean off the area the gasket goes?

Sure, brake cleaner will work too - but scrape it down to bare metal first. The gasket material is REALLY tough stuff. I like to sharpen a putty knife with a file to a razor edge and scrape with that. I have found it advantageous to be able to tap on the end of the putty knife with a small hammer when going through the tough stuff, so get a putty knife with a blade that goes all the way through the handle with wood riveted on both sides.

If you're a "Super Lucky Ace" and all the stars align correctly and the moon is in the third house the gasket might be stuck to the cover and come off the rear end housing clean. But I have never ever seen that happen!! Chances are it will be adhered to both the cover and the rear housing - and will tear around each bolt hole leaving super hard gasket material there. Not a big deal - just be prepared to work at it and make sure surface is clean and down to metal.

FYI - now is the time to replace your disk brake backing shields if they are rusted off. Axles need to come out and this cover needs to come off for that to happen.

How long can I leave the differential exposed? I'm going to try to remove it tonight, but doubt I'll get it all done by days end. There is no rain in the forecast until Thursday and it will be in a garage just in case it does rain.

Also never left the Blazer rear end on stands for this long. It is safe for it to just stay jacked up for a couple days right (I'm left to assume yes, but better safe then sorry)? Potentially putting entire car on 4 jack stands for other work (2 2-Tons for rear, 2 3-Tons for front). Makes it easy to slide around under the truck if it is all lifted as high as I can. Where are good points for the stands? I usually put them on them right next to the scissor jack hole (the spots where the provided jack bump fits nicely) on the frame. However I have never lifted the whole truck like this before.

Should be fine leaving the cover off over night. The residual diff fluid on the gears will prevent any surface rust. The garage is going to smell like gear oil though lol

Put the rear axle on jack stands and the front frame rail on jack stands. Have done it many times, never had an issue. Most recently was when I did the brakes on my father's F150, did all 4 at the same time so I only had to make one trip to a guy he knows that owns a shop to have all the rotors turned. Sure looked funny in the driveway lol but made it much easier.


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Well, tried to remove the plug yesterday with a foot long ratchet with no luck, it slipped right out. Only tried once, it was getting dark and I didn't want to strip the plug any more. Going to hammer in the drive extension tonight and hope for a better grip. Any other tricks to getting this thing off?