The rear pinion seal on my 12 bolt is leaking like crazy. While mechanically inclined I have limited experience working on differentials. Locally they want $80-$100 plus parts to install a new seal and possibly yoke. How difficult is this? Are their any special tool or procedures I need to follow? Of course the local shops lead me to believe this is somewhat difficult. To me it seems like a rather simple fix, but I don't want to risk thrashing a 12 bolt over $80.

Thanks in advance

The problem with replacing the seal is that underneath it is a crush collar that compresses when the pinion nut is tightened down. When you initially set up the gears, you squash down the collar until you get the proper preload on the pinion bearings.(this usually takes a breaker bar with a cheater pipe). When you take the nut off, you lose the preload, in turn changing the pinion depth, which changes the set up of the gears. I believe some people don't worry about that and attempt to mark the positioning of the nut and tighten the old nut and collar back down to that point after installing the new seal. (rather difficult to do). The correct way is to get a new crush collar and nut from your local dealer and reset the preload on the pinion bearings. The problem with this is that, (anyone correct me if iI am wrong) you set the pinion bearing preload without the ring gear in place, so that would require taking the carrier and ring gear out. The preload is set by using a 1/4 inch beam style torque wrench adapted up to the proper size of the nut. Be sure to check the yolk to make sure there is no damage or grooving in the seal area. I hope this helps and my intentions are not to scare you from doing this job yourself.

I replaced mine with no problem. Seal the splines with a little rtv and also around the outside diameter of the seal before installation. Also remember to grease the seal so it doesn't start dry. Buy a new nut and use a little locktite for insurance. You can crank pretty hard to tighten it without further crushing the sleeve. It takes about 100 ft. lbs. to futher crush the sleeve. Do a search. This has been answered many times. Good luck.

I'll try to save you a little search time; I did this a month ago. I saved these links.

http://www.camaros.net/forums/showthread.php?t=57222&highlight=pinion+seal+leak
http://www.chevelles.com/forums/showthread.php?t=81102&highlight=pinion+seal+leak
http://www.chevelles.com/forums/showthread.php?t=70517&highlight=pinion+seal+leak
http://www.chevelles.com/forums/showthread.php?t=66455&highlight=pinion+seal+leak

Receintly I checked a 12 bolt to see how much torque it would take to crush a spacer enough to change the bearing preload while changing a pinion seal. I torqued the nut to 250 foot pounds before the bearing preload changed 2 inch pounds. When changing the seal you should be safe up to 150 to 175 foot pounds of torque on the pinion nut without cahnging the bearing preload. Use sealant around the outside of the new seal and in the splines of the yoke. Use grease on the lip of the seal and lock tight on the pinion threads.

As always thanks guys for the help. Looks like I will be doing this myself. Just need to get a pinion seal , nut and yoke. Thanks again.

The pinion seal that is sold for the 12 bolt car is not the original. They don't make the original seals any more. I have had some trouble with these. They want to go in too far and contact the outer pinion bearing. You might have to leave the seal sticking out about 1/8 inch to keep it from contacting the bearing. Check it out as you are driving the seal in.