Differential Oil Seal Question: 90 GMC truck

SNIP

You drain the diff by removing the stamped steel cover on the back of the housing.

To get to the pinion seal you will need to remove the whole carrier and ring gear assembly, then the pinion.

Reassembly requires a dial indicator, big torque wrench and an acquired "feel" for it.

Not a job for a beginner unless you are willing to do it over and over until you are able to reassemble it without leaks or undue noise.

"yoke"

Yes. You will need to retorque the yoke for a slight preload -- felt as a slight stiffness -- and that's a little tricky. The proper procedure will involve removing the outer pinion bearing and replacing the collapsible sleeve that goes between the inner races of the front and rear pinion bearings. The purpose of the sleeve to give the big nut that holds the yoke on something to bear against to keep it tight. The sleeve can be replaced without removing the gears or the rear cover. Go to the dealer to buy the sleeve and the seal and have them print out their exploded picture. While you will probably end up over-tightening the pinion bearings slightly, you can get away without replacing the sleeve although this is not by the book. If you do it right and replace the sleeve it will take MUCHO torque to tighten it down to where the pinion doesn't wobble plus a slight preload. If you over-tighten the nut ideally you should start over with a new sleeve. If you don't the nut has nothing to tighten against. So go a little at a time once all play is out of the pinion. There should be barely perceptible stiffness or drag.

Don't worry about draining it if you don't want to. Just catch whatever comes out when you remove the yoke and top it up afterwards.

Don

I didn't realize that you don't have to reset the "end play" of the ring gear after removing the yoke from the pinion gear.

That 'aint as bad to tackle then!

You needn't do anything with the ring gear at all. In fact while the book might call for re-doing the whole setup, you can replace the pinion bearings and the even ring gear carrier bearings without a problem. You must leave use all the original shims in the original positions and mark adjustable carrier bearing retainers if used. The ring gear backlash and pinion depth will be fine. I have not yet created a "whiner' doing this.

Don

I think you'll get there!