Replacing rear end pinion oil seal...
 

I'm trying to replace the pinion oil seal on my '83 GSL differential. My goal is to not do a complete teardown of the diff.
I've marked the nut, pinion shaft and companion flange to ensure they go back together with (hopefully) the same bearing preload.
The nut is off, the washer is off -- the companion flange does not want to come off.
I've tried light tapping with a dead blow hammer as I rotate the pinion assembly. I've tried a puller (fairly tight, but haven't gone full-gorilla with it yet).
It does not seem to want to budge. Videos I've watched (of other styles differential) generally show the flange coming out rather easily.

So am I missing something (nothing special indicated in the service manual)? Is there a trick I'm missing? What's up?
https://cimg9.ibsrv.net/gimg/www.rx7...c01eaa98c6.jpg

Other info, in case it matters/helps:

• rear end is out of vehicle
• oil has been drained
• diff not opened up in any way
• axles are out

Thanks in advance for any suggestions...

Do you know when the last time it was off? The splines might have rusted a little. Maybe try some penetrating oil and a little more hammer.

Pretty sure the last time it was off was when it was put together at the factory...
I did put some penetrating oil around the splines - it seemed to flow in pretty easily (a small pool disappeared fairly quickly)

I just took one apart a couple of weeks ago and it took quite a lot of force to remove the flange. The puller is the safest way to remove the flange but they can be removed with a hammer (dead blow) but it is much more difficult. If you use a hammer I would recommend putting the nut back on the pinion to cover the threads so you will be less likely to damage them. Also, use a brass drift or other soft material between the hammer and threads. I actually used a 3/8" piece of aluminum plate I had laying around The other problem with using a hammer is you will need to support the weight on the flange with the 3rd member or rear end off the ground or work surface. (Because you are driving the pinion off the flange and it has to have room to move away from the flange). USE THE PULLER would be my advise. If your puller has a good hold on the flange, tighten it as much as you can. It's gong to be really tight. If the flange doesn't move then strike the end of the puller (where the socket or wrench goes) with a hammer. You may have to hit it pretty hard. The sharp blow from the hammer will usually cause the flange to move. Tighten the puller and repeat if necessary . Normally I have not had to hit the puller again once it begins to move but you may have to use the puller to continue to move the flange off the pinion. There may be other techniques but this has worked for me When I say hammer I am referring to a dead blow hammer or 2 lb mallet, not the kind you would use to drive a nail.

Penetrating oil and puller is the way to go...
I see no way of setting the pre-load right again without tearing the complete mo**^^$fc*ù again and buying a new crush sleeve.

Believe me, I am in this painful process of assembling a 4.777 diff and I have now assembled/dissassembled the thing 4 times to get the right shim.

Ok, got it off... used a puller and had to use the impact wrench to get it off.
Everything was nice and clean, splines looked fine on both the shaft and the coupler - no galling that I could see, just a very tight fit.
Replaced the seal and got everything back together - the coupler went back onto the shaft without any real problems, was able to tap it most of the way on with a dead blow hammer (nothing extreme).
It did take a lot of torque to get the retaining bolt back to its original position, but it's all back together and in the same relative positions to each other as when they started.

I had concerns about that as well. I'm sure that's the better way to do this, but from what I've been able to glean from the web, this approach appears to be pretty standard operating procedure...

Yeah, that's standard trade practice.

If you do this in the future, another thing you can do is measure the rotating torque before you take it apart, and then remeasure when you put it back on. If the rotating torque is higher than when you started, you went too far. It's a good thing to sneak up on.

I wonder if the torque produced by the oil seal and the bearing preload is big enough to have an influence on the torque value when your rotate the whole assembly?
I'll check when I reassemble it.