Thanks terry s.

When I did the work last year, I removed every bit of old gasket with a blade, then sanded the surfaces, then when I went to put the cover and gasket back, I applied the RTV all over including around the bolt holes, then the gasket and put all the bolts on tight. I don't think it was leaking initially but don't know exactly when the leak started, until I started noticing drops on the driveway everywhere I parked the Jimmy! I looked under there several months ago and couldn't see any dripping so I left it. Since the dripping continued I looked under there again and then found a small drop of lubricant at the bottom center of the differential. Wiped it off and tightened the bolts a few degrees only. Checked it again several days later and found a new drop on the differential, tightened again a few more degrees of rotation (very little) but the drip continues.

I wonder if perhaps the cover was deformed slightly as I pried it off! They're not made of metal all that thick.

I will try the silicone bead on the outside as you suggest and pray. But, I fear I may have to replace the cover, gasket and fluid to stop the leak.

I know I haven't lost much lubricant yet because the leak is very small, but over time this leak spells trouble. I once had a pinion seal replaced by the dealer on a Monte Carlo back in the eighties, then went on a road trip up and down the Cabot Trail (Nova Scotia) and on the way back my rear end burned up because the dealer had not topped up the fluid adequately - I had to get the car towed to a shop that installed a used whole rear end to enable us to finish the journey home! A new rear end would have cost much more and take several days to get. I don't want to go down that road again so living with the leak is not an option for the long term!

 

Yes the cover could have been distorted. As I recall I don't think you are supposed to use RTV with a gasket. Are you sure it is not the pinion seal leaking and blowing back on the housing?

I am not a fan of this but some differentials come from the factory with only RTV and no gasket. You could try that or you could replace the gasket and use a gasket sealer that is made for use with a gasket.

 

Mine definitely had a gasket that did come apart as I pulled on the cover plate and that was the reason I had to use a blade to get all the pieces off.

I don't think there would be any problem with combining the RTV with the gasket!

But I will definitely check the pinion seal, for that could be the problem this time around, with blow back as you suggest. I never thought of that! I just saw the drop on the lowest part of the differential where the cover is and assumed it was leaking there. I had the vehicle undercoated with dripless oil last year, which makes it tougher to see the origin of the leak; so I'll have to clean the area, take it for a drive then check again to see if there is any lubricant coming from the pinion seal.

Thanks bud.

 

Shucks, it looks like it is the pinion seal. At least that makes me feel better about the job I did last year!

Although it's hard to see because the vehicle was undercoated with an oil/wax mix, the area underneath the differential did look oilier all over the bottom surface than the rest of it. I've wiped that area clean to the touch with a rag and will check it again in a couple of days to see if it's really oily again, which I expect will be the case.

In the meantime, can anyone point me to a good detailed procedure to replace the pinion seal on this vehicle?

Thanks

 

Yep, it's my pinion seal.

Before I start this job, I'd like to make sure I have all the stuff I will need.

Right now, I don't know what size of ratchet socket I need to remove the pinion shaft nut; I have lots of sockets but only one that is greater than 1", it is a 1-1/8 socket, so if that isn't the correct size I would like to know what size I need so that I can pick one up in advance.

Also, there are a couple of sizes for the rear pinion seal, the 7.625" and the 8.5". I'm hoping the dealer can tell me what size I need from the vehicle's VIN number. If there is an easy way to find out that information before taking the seal out, please let me know so that I can buy the correct size in advance.

Thanks

 

The dealer should be able to get you the correct seal from your VIN. I don't remember what size socket but you should get a new self locking nut anyway so you can see what size it is then.

If the seal is not a rubber coated one I always clean the seal and the inside of the housing where te seal goes real good with brake cleaner. Then apply a thin coat of permatex hi tack gasket sealer on the seal and inside the housing. If you don't do this it can seep between the seal and housing if there are any imperfections. Also clean the end of the pinion splines and the end of the yoke splines real good. Before you put the washer on put gasket sealer around the end of the splines because sometimes it will seep grease past the splines.

The nut should be very tight. You will need a lot of leverage to get the nut loose and to get it tightened properly. Do you have a manual for the proper tightening procedure? Make sure the area on the yoke where the seal runs is not groved or damaged or it may leak even with a new seal.

 

Thanks, terry s.

No I don't have a manual for the correct tightening procedure. I watched a video on line and the fellow in the video just counted the number of threads beyond the nut to the end of the shaft and marked the nut and shaft to see where to restore the nut to. Is that not enough?

I've been looking for a detailed procedure but can't find one specifically for this vehicle on line.

 

What year do you have. I have a manual for a 95 but you can't follow it because you tighten the pinion nut and check for a specified preload by rotating the pinion with an inch lb. torque wrench. To do this the ring gear carrier is not installed. This collapses a new crush sleeve until the correct bearing preload is obtained. Since your crush sleeve has been collapsed and you can't check for preload with the ring gear in place the best you can do is to tighten the nut until all slack is taken up between the u-joint flange and the crush sleeve. Follow the procedure you mentioned but make sure the new nut is exactly the same thickness as the old one. Barely start the old nut on the pinion and see where your index mark is on the nut for rotation. Then do the same with the new nut and mark the same spot on the new nut. A center punch works good for marking the nut so you don't wipe off a mark. I hope this makes sense.
If you can't get the truck up high enough to get a long pipe on your break over bar you may not be able to get it loose or to get it tight enough. I have used a large pipe wrench on the flange and let it rotate until it hits the underside of the truck to hold the flange. I do not recomend this but I have had to use a jack on the end of a break over bar to loosen and tighten the nut because I was working only with jack stands. I don't know for sure but I think it takes well over 300 ft. lbs. Good luck.

 

Thanks again, terry s. Yes, you make a lot of sense.

Mine is a 2005 brought back by GM for the Canadian market only, but understand that it's identical to the 2001 you would see in the USA.

You are certainly bringing a lot more to the fore than the fellow did in the video. He simply used an air ratchet to remove and put back the nut and the whole thing appeared quite easy.

So the crush sleeve is the reason I will need a new nut. The guy in the video just re-used the same nut.

I called the dealer to price the parts and the nut sells for more than the seal - obviously not a regular nut!

If I need to apply so much torque (more than the truck engine can deliver to the wheels, lol) to remove and replace the nut, I will indeed need a lot of space. It sure would be nice to have a pit in the garage, but unfortunately I have a flat garage floor, and don't own a torque wrench, and it's up in the air as to whether I will even have the right socket for the nut.

Maybe this is one job I need to take the truck to the garage for where they can hoist the sucker up in the air!

It's just I've had such poor luck with service garages, I dread going to them.

 

Here is how the preload works. If you had a new crush sleeve and you started tightening it down when the nut took up all the space and felt tight the bearings would not be against the races and you could move the pinion back & fourth. As you tighten the nut the crush sleeve has a bell shape in the middle that squeezes together to allow the bearings to finally touch the races. The crush sleeve gets shorter as you tighten. Then you keep tightening until it takes XXX inch pounds of torque to rotate the pinion. Then you have the correct preload on the bearings. The nut is a self locking nut because if the nut backs off the bearings will not have the correct preload which will shorten their life but worse yet if it backs off far enough the pinion can move front to back and it will destroy the gears.
I like to use a new nut to be sure it will not come loose. Some people use locktite whick I suppose is ok but a nut is cheap insurance in my mind. If you just put the old nut back on you risk having it come loose.
The old crush sleeve will have collapsed to the correct preload when new. It will slightly lengthen when you take the nut off and the bearings will have worn slightly. So ideally you want to tighten the nut back where it was and just a tiny bit more.
If you can safely get the truck up on some tall jack stands give it a try and see if you can get the nut loose. If you can you should be able to get it tight enough. I have actually had a craftsman 1/2" break over bar bend when using a jack to tighten the nut one time. The break over bar sprang back and was ok but I really thought I would break it. I have actually snapped the square end off on one using a pipe for leverage trying to loosen a front axle nut once. If you have access to 3/4" drive break over bar that would be better. Use safety glasses to be safe in case it breaks.
I know what you mean about finding a good mechanic. Ths is one of those deals where if they are not careful and don't know what they are doing it could cost you a differential. GRRRR There will not be a problem for a while and there is no way they would admit it is their fault.
Good luck and let me know how it goes.