I got a lot of practice at this job when I was building v-8 z cars back in the day... /ubbthreads/images/graemlins/rofl.gif
One trick I learned from a saavy old gear vendor was to was to make some witness marks from the shaft to the flange to the nut with a touch up paint pen before you take it apart.
If you're re-using the nut, not recommended!, (but often done with copious quantities of the correct grade of loc tite... ) and you clock the flange back on the shaft in the same location, when the line on the nut aligns with the witness marks on the shaft and flange, you're in the ballpark torque-wise. This is handy when the diff is out of the car and you don't have an easy way to hold the pinion to torque it correctly. To do this job correctly, you can make a fixture that bolts the companion flange fairly easily, but it still looks like monkey's f***ing a football as you chase the thing around the bench... (these pumpkins are easy compared to many I've done in the past!)
Remember, you're setting the preload on the bearings when you torque the flange nut down. Take your time and do it right!
It usually works out just fine if you end up a red curly hair tighter than the original witness mark, but your mileage will vary.
Since you have the car there, you can do it the easy way and just replace the seal without dissassembling anything else.
Pop the driveshaft flange off, support the driveshaft with a couple of bungy out of the way.
Set the e-brake firmly
Mark everything, and using hand tools =socket and breaker bar=, remove the nut (**cheater bars allowed if you're a Nancy boy, just don't blast it with an impact!**)
Slide the flange off, and inspect the sealing surface. Deep grooves/ugliness means a wtb add.
Using a small, sharp awl (or a nail /ubbthreads/images/graemlins/tongue.gif ) poke a hole in the seal face, more towards the outside edge.
Thread a small sheetmetal screw into that hole. The bearing is only about 1/4" back, so don't go crazy screwing the damn thing in.
Gripple onto the head of the screw with some vice grips, and lever/pull the seal out.
You can also use a t handled seal puller, or a screwdriver/prybar, but I like ^^this^^ way the best, becasue you won't scratch/damage either the flange or the case.
For best results, clean the sealing surface on the companion flange with soft scotchbrite. If it is grooved a little where the previous seal cut into it, be sure to get a seal with a different following letter prefix. (the seal manufacturers are fairly saavy, and they change the location of the sealing lip a schosche, and identify those seals with a higher following letter. I.E. 1773c versus 1773a /ubbthreads/images/graemlins/wink.gif )
Do not spray any cleaner into the front case/pinion bearing recess, as it will contaminate the front bearing. Just wipe clean with a lint free towell.
With all the halfshafts still installed, just install a new seal (after throwing a little assembly lube/grease on the sealing lip /ubbthreads/images/graemlins/wink.gif ), spin down a new lock nut with hand tools, lock the handbrake, and slowly sneak up on the middle of the torque range.
The factory spec is 116 to 159 ftlb's
Fill the diff with your favorite flavor gear oil.
Done
**For those with access to power tools, don't attack the pinion nut with an with an impact gun if you don't want to see what pinion bearings look like. /ubbthreads/images/graemlins/idea.gif
The whackity whack whack of an impact will brinell the ever loving dog sh*t out of the pinion bearing races and the bearing races will begin to deteriorate shortly thereafter...