Pinion seal replacement?

[CJ Johansson]

OK folks, looks like I need to replace the pinion seal (where the driveshaft enters the diff, right?) on my '98 3500. It's got quite a trail of oil running down the front of the diff, and leaves oil spots wherever I park (luckily, at home it's mostly dirt, soon to be covered by gravel I hope, so the spots are no big deal to me).



Anyway, I'm looking for some pointers on how to tackle this job. I've never messed with diff's much, but I have replaces plenty of seals on axles, etc. , is the pinion seal similar? Looks like you have to take the U-joint apart and remove a big nut to get the remainder of the U-joint off.

Do you have to open the rear of the diff, or can it be done from the front/outside (I'll probably open the case and change the oil anyway since it's pushing 100K).



Anyway, if anyone has some step by step instructions I'd sure appreciate it. A list of "gotcha's" and things to make it go easier would be really nice!



-cj

 

[drrhoades]

I have been working on some rather large Case tractor axles lately, tearing them completely apart and rebuilding them. If you try to push out the seal you will have to take everything apart which means that you have to reset the backlash which is a real pain. I would think that you would be able to undo the pinion nut and pull the coupler off of its shaft. Then you should just be able to take a large screwdriver and pop the seal out. This is the easiest way to do it. I have done both. When reinstalling the seal make sure that it is seasted evenly all of the wasy aroundBe sure to check the backlash though and make sure to tighten the pinion nut to the speciefed torque. LIke I said I have done this on tractor axles not Dana 80s. But I imagine that they cant be much differnet Someone will say something if I am wrong.



Doug

 

[Extreme1]

I wrote a rether lengthy response to this same question a couple weeks ago. Long story short:

You need a puller to remove the yold from the pinion shaft.

The nut is on at 450 ft-lbs. Mark the nut and shaft and tighten back up with a large air impact wrench to the same place or a little more.

Don't worry about the backlash, no effect.

Grease the seal lip before installing and apply a thin layer of sealer to the outside edge.

 

[dremelts]

I've never done this repair myself but I seem to recall seeing something in the Chilton's manual about the big washer behind the nut being slightly convex (or concave depending on how you're looking at it), and to make sure that you get the washer back on the way it was.

 

[Dfeland]

I would check your pinion bearings while you are there, generally seals fail for a reason. Just for FYI.

 

[DarrellB]

One more suggestion

I had my dealer replace mine. I have a very good dealer though and their mechanics are really good. They only charged me about $62 to replace the pinion seal and it only took about a half hour. It was well worth the $62 to have it done in that amount of time. You might want to ask at least, it can't hurt to ask.



Big D

 

[Extreme1]

Check the pinion bearings!

Yup, Joe D. wrote an article in issue 24 about rearend (get it if you don't have it). He said most of the time the seal leaks because the bearings are shot. You should check them with a dial indicater on the shaft, and try to move the shaft up, down sideways, etc. I don't think you should see any movement on the indicator.



When my seal leaked, I replaced it and all has been well since.



If they are bad, you should do the carrier bearings and check the hub bearings.



You can do bearings in your driveway (I installed an LSD), but you will need a puller for the old carrier bearings. You won't have to go through any set up proceedures, just put all the shims back where they were. The bearing tolerances are sufficient to maintain correct gear contact.

 

[CumminsPower98]

Pinion seal

I replaced my Dana 80 pinion seal a few months back. Everything was tight and in good shape. The seal just wore flat and seemed a bit soft for some reason. My mileage was not even that high so I think some seals just fail prematurely for some reason. I used a puller to remove the yoke and then used a large screwdriver and hammer to get the old seal out. Be sure to use a little RTV on the outer edge of the seal to be sure it does not leak out there. I used a 3/4" air impact to put it back together since I don't have a large enough torque wrench. I didn't mark where the nut was before I took it apart but it really isn't that critical as long as you torque it to at least 450-500 ft. lbs. A little tighter then specs is not going to hurt anything as long as it's not excessive since the pinion preload is setup with shims rather then a crush sleeve like some. I'm not an expert but I have rebuilt/setup quite a few differentials.