usmilret

I know how to change out a rear differential seal; However it looks to be tight just to get to.
If you changed one out before and found a better way to do it, if you could please enlighten me. I thank you in advance.

usmilret

For those who would like to replace the rear differential input seal.


Raise the car up on jack stands, the higher the better.







Take a pry bar and fir it in between the input shaft and the seal and pry like a banshee. I used leg power to pry the seal off.







To make a seal driver I welded an old 3/4 drive breaker bar to stay straight and cut it to length. I used a 1"drive socket to fit over the new seal.







New Seal installed into the read differential. The job wasn't as difficult as I initially thought.

babbah

you are speaking of the rear differential seal that the driveshaft input yoke slips on spline shaft of the pinion gear, yes?
Mine is a 67 but I think yours is the same on your 1982?
I read all the horror stories about removing the input yoke that has a big nut that tightens to the pinion gear, that it is possible to crush the pinion bearing if that nut is tightened too much.
They say it has to be marked before it's removed. Idols to replace mine while the diff is in the car -
I don't see anything regarding that in your process so I am curious to ask. Also the diff carrier with the snubber bushing is right under the carrier so does that have to be removed, if so how?
Can you provide the preliminary steps of this process as well? Than You - Very helpful post.

usmilret

I didn't mark the yoke before I removed it. I can also tell that the previous owner didn't mark it as well.
It is possible to over torque the yoke. I just snugged it down to where the yoke had no play.
The preliminary steps that I followed were..
1. Mark the driveshaft for removal and remove the driveshaft. . I am sure that the former owner didn't when he removed the driveshaft before.
2. Remove the yoke. I had to take a hammer and a brass drift to tap it out.
3. Pry the old seal out with a large pry bar. This took quite a bit of strength to do. I used my foot on the pry bar.
4. Clean the area where the new seal goes.
5. Install the new seal with a seal installer.
6. Reinstall the yoke and washer. I don't know what the torque specs are.
7. Reinstall driveshaft.

You will lose a lot of rear differential fluid when the yoke comes out.

babbah

Thanks US - So you did this while diff was in the car -
1. What about the carrier mounting bracket under the diff with the snubber bushing? Didn't you have to remove that as well? or no?
If you did how do you get the mounting bolts of that mount out since they hit the interior buckets. Is your diff and mounting the same as in a 67 car?
2. Where do you tap it with the drift? From back or side, or?

68blvert

I'm not trying to sound like a know-it-all but if you didn't measure turning torque at the pinion flange, with the half shafts removed, you are never going to get the proper preload set on the pinion bearings. There is no tightening torque spec for the pinion nut per-se. While it takes alot of force, around 180-230 ft lbs to set proper preload on a new crush collar the final set is to creep up on the turning resistance measured with an inch lb torque wrench that reads in single digits. This is also done without the ring gear installed and the pinion gear depth set. This is how it's done on diff overhaul. Turning resistance will be different with and without ring gear installed which is why you must measure turning resistance before disassembly. All published turning resistance value are given without the ring gear installed. You can probably get it close by "feel", but i've rebuilt many ruined diff's for guys who tightened the pinion nut by feel. Like I said i ain't trying to mock or embarrass you just thought you should know.

mikem350

The snubber does not have to be removed, but it is a PITA to work around it. I used a LONG socket extension bar to tap in the new seal, two person job. Just the bar, I did not have a big enough socket to fit. I would strongly suggest doing this job on a lift!!!!

Remember to use sealer like Permatex #2 on the pinion threads or you will have a leak there

usmilret

69blvert
Thanks for the advice.

I will keep an eye on it.

I removed nothing other than the driveshaft. I didn't remove the snubber bushing. I didn't remove any mounting bolts.

Again I will keep an eye out for leaks.

Vince'82

that's true for previous years, but 80-82 diffs don't use crush sleeves for pinion preload.
on 80-82 diffs, we use shims and there is a tightening torque for the pinion nut.

68blvert

My bad your, your right about shims. Stupid me wasn't paying attention to year. But some of what I said still holds. The 80-82 diffs pinion bearing preload is still set by measuring rotational torque at the pinion nut without a ring gear installed. Pinion preload on those diffs are set by tightening pinion nut to 210 ft lbs and then measuring rotation torque which should be between 15-35 inch lbs. proper preload is attained by removing or adding shims and remeasuring. The reason i say you must measure before dissasembly is because the factory spec don't hold true when your turning against the ring gear, case bearings and weight of then case assembly. just trying to help.

usmilret

Yep, theres a leak there. The pinion threads are leaking. You were dead on.

usmilret

Thank you for the advice. I made the mistake of not torquing the pinion nut using an inch torque wrench. Learned my lesson there. Output shaft seals have to get replaced. Like a previous poster said "It is much easier when you remove the read differential from the car. While I am at it there is a build sheet on the fuel tank. I will be dropping the fuel tank to get to it.

This is a 34 year old car with 34 year old seals. Put about 1000 miles on the car and seals are leaking everywhere it seems. This car sat for 10-11 years in a garage. Remember that when you buy one of these C3s. Transmission shift seal, servo seal and output seal. Input and output rear differential seals.