Hey folks,
My younger brother has an '86 IROC with a stock 10 bolt rear. We need to change his rear pinion seal. I've looked through his shop manual as well as the shop manual for my '90 Firebird Formula but have had no luck finding step by step directions on how to do this. If any one has any leads on how to do this or where to find step by step directions any help would be greatly appreciated.

Thanks,

FirebirdBrtha90

 

remove the yoke
pry the seal out with a flat screwdriver or similar device
tap the new one in with a hammer and drift pin
re-install yoke to proper specs
re-fill the diff with fluid

oh did i mention all the diff oil will come out?

thats the basic idea

 

Obviously drop the driveshaft, 4-bolts on the straps that hold it to the yoke. Then what 86TA said. The specs for re-installing the yoke is 6-7 inch pounds since the crush sleeve is already pre-loaded from B4. This spec is for the 7.5/7.625 diff. f you have the Dana44 (most likely not) or the Borg 9-bolt (possible) it might be a different spec. Also when breaking the pinion nut loose, hold the yoke while doing so...dont use the gears against each other to break it.

 

i always measure the distance from the end of the pinion to the nut and reinstall it to that distance and add one flat on the nut. use a new nut they aren't suspose to be reusable. lube the seal or you'll fry it when you first spin the DS.

 

Thanks for all the info guys and/or gals! It is much appreciated.

 

This is not entirely correct. The 6-7 in lbs is a rolling torque value for used bearings. You would have to disassemble the rear entirely, including taking the carrier out, to check this value. Most people mark the nut in relation to the yoke, take it off, replace the seal, and tighten the nut back to the same point.

You do not tighten the yoke to 6-7 in lbs! You will lose your pinion very quickly if you do. The nut will get 150+ FOOT POUNDS of torque in order to reach 6-7 in lbs rolling torque. However you will probably not be taking the rear far enough apart to check rolling torque (although it is the only really legit way).

 

All of the replies so far have good advice in them. It is absolutely critical that you get the nut back where it was before you removed it. For this reason, even though everyone recommends a new nut, I'd say to go ahead and re-use the old one. If you don't get it back to the same place, the new seal can end up leaking worse than the old one, and your gears will clunk due to excessive backlash between the ring and pinion (i.e. improper bearing preload). Just make sure to clean up the nut and the pinion threads with brake parts cleaner and use a little red loctite on the nut before re-installing it. This will keep it from coming loose again. As far as making sure to get it back exactly where it was before, count how many threads are sticking out of the nut before you loosen it, and use a sharp chisel to make a line in the nut and the pinion threads. There's usually a little slack in the bearing preload on an old setup, so I usually tighten the nut about 1/16" of an inch past the original mark that you make with the chisel. In other words, just a hair tighter. Also, as mentioned above, make sure to put a little oil on the rubber part of the seal before installing it to avoid it getting burnt when the yoke spins. A short piece of 2-1/4" or 2-1/2" exhaust pipe works great for driving the new seal in without damaging it. You can buy these at the parts store when you get the new seal. In fact, just get a 2-1/2" to 2-1/4" adapter fitting, and you'll have both sizes in one piece. Pinion nut size is either 1-1/16" or 1-1/8". I've done several pinion seal replacements this way and haven't had a problem yet. Btw, 327_TPI is correct. You can't accurately measure the pinion bearing preload unless you remove the carrier from the rearend. That's why marking and re-using the old nut is the best way to do it without a lot of extra hassle.