xavier

I just recently changed the fluid in the rear differential of my truck and unfortunately the next day I noticed it was leaking. It appears as if it is leaking from the seal because the housing is dry. I changed the fluid using Mobil 1 75w 90 gear oil and I replaced the gasket and used black rtv sealant. Anybody have any ideas? My truck is a 2001 Silverado 1500 LS 5.3L 2wd. It has the GT4 differential. It asked for 2 1/4 quarts and I may have put in slightly more than that, but not by much. It was still under the fill hole and the additional amount wasn't much.

Thanks in advance for the help!

Camaro 69

The fill hole is also the spill hole. When the oil starts running back out, it's full. Could be your level was low with the old oil, and being up close to the right level now is showing a leak that you already had.

GMcerttech

looks to me like a pinion seal gone bad. ive seen it happen before when people change the oil after it hasnt been changed for a while it cleans out the dirt and grim around a seal causing an old leak to show up. that dirt and grim use to plug the seal. ive only seen it a few times though

xavier

I think you guys are right and that is what I was afraid of. My truck has 138k miles on it and this was the first time I changed the diff fluid so I'm not surprised this happened. I guess I will have to look into replacing the seal. I've looked into it a little bit and I hope the job isn't beyond my means.

Thank you for the quick replies.

ericnottelin

How'd you do. Changing this seal is not very difficult at all. A basic socket set and an inexpensive seal puller and your there.

Eric

xavier

To be honest I've been so busy I haven't had time to fix it yet. The leaking has slowed and at this point there isn't much coming out anymore. I've checked the level through the fill hole with my finger and when I point it down I get fluid on it. It is definitely the seal and I've asked a friend about it who is a mechanic and he said he had a bad experience fixing one in the past. I may just pay the $100 to have it fixed and have peace of mind knowing it was done right.

kevinkpk

Drop drive shaft. Pull yoke. With either a seal puller or screwdriver hammer reomve old seal. Clean the sealing surface with crocus cloth, and clean. Install new seal, with a piece of pipe the diameter of the seal outer metal surface, and hammer gently tap the new seal in till it is seated, reinstall yoke drive line.

Or pay the 100 bucks.

ericnottelin

Xavier, The level of fluid should be to the point that it is just below the fill hole when level. IE, you fill it up until it starts to overflow then place the plug back in. If it is below this level, you stand a chance of over heating the rear gears / under lubricating them. Sounds like you ok FOR NOW. However, I would not wait long or drive it much until it is resolved. A $100 sounds about right. You will basically drain about 1/3-1/2 of the fluid you have in there now when you pull the yoke / seal. So you will have to pay for the new seal, the labor and probably 1 qt of fluid (they won't use that much but they always round up!).

I regards to your mechanics statements, one can always find someone that has had a hard time with something. There are always SNAFUs. But for the most part, this is relatively an easy fix. If you did the diff fluid swap yourself, you could definitely do the seal. You may find it easier than the fluid swap itself. Not much to clean as the seal usually (notice i said usually) comes right out. I would definitely recommend a seal puller. Makes life a whole lot easier. You can use an over sized socket to tap the new seal back in. If you don't have one, you can just gently tap in a circular motion around the seal (similar to a hub bearing cover) until it seats. This is actually how I have installed over 90% of my seals.

Best of luck

Eric

Camaro 69

Do not, I repeat DO NOT simply pull the pinion nut and yoke and put it blindly back together. If this is how your mechanic friend did it, I can see why he had a bad experience.
Take a sharp chisel and hammer, and make a reference mark lining up the nut, the yoke, and the pinion shaft. Then count the number of exposed threads at that mark. When putting it back together, make sure you have the same number of threads exposed as all those marks are lined back up. This will put you right where everything was before you took it apart. Slapping it all together *****-nilly will alter your pinion gear to ring gear depth, which can spell premature gear failure.