GM 12-bolt pinion seal leak - CAN I DO IT?

[davepl]

I took my B-Body in (with a GM 12-bolt) for a laundry list of little things but my favorite mechanic demurred on the pinion seal leak because he wants me to take it to a differential specialist. He doesn't want to touch the backlash and so on.

Does replacing the seal require disturbing all of the preload and so on? I'd rather not take this car to the far away drivetrain shops if I can avoid it, but don't know all what's scary about a pinion setup (hence, I should take it in, and likely will, but am still curious and want to learn).

What's the actual procedure for fixing a 12-bolt pinion leak? Anyone know? Anyone done it successfully?

[AussieinNC]

The work involved in doing it yourself is minimal...usually about two hours...

Preload is relevant in two locations, one on the pinion gear and one of the carrier bearing set....

I always drop the rear cover off and check the rest of the gear set etc, If it needs other work, send it to a diff guy...

if the rear end is otherwise ok, no noise etc, you can usually remove the flange and seal without too much trouble.

If the pinion has more than 1/8" of side to side movement the rear end needs to be done professionally.

The pinion flange needs to come out which means removing the driveshaft at rear universal joint, then removing the nut holding the pinion flange on.

Removing the pinion flange will remove any preload that exists on the pinion bearing assembly. Sometimes you need to use a puller to remove the flange.

Check the flange area where it runs on the seal lip...if its grooved either the flange should be replaced or re-sleeved to restore the seal surface. New seal goes in easily but suggest you pack the back of the seal lip where the spring rides with grease to keep spring in location while its being installed.

Replace the seal and pinion flange, and tighten the pinion nut to its original position.

Dont use an impact gun as you will over tighten the nut...pull the nut up until all side to side movement of pinion is removed, then tighten 1/8 to 1/4 turn more.

Hope this helps..