I just climbed under there to take a look at both differentials before I did anything and this is what I found in the rear:

What the heck? Is this from a bad seal?

 

Look like a bad rear pinion seal.

 

Finished the front diff, and then started cleaning up the rear. Drained 1/2 quart of the front and put in 1 qt 20 oz, so it was definitely overdue.

I'll tackle the rear tomorrow/ I figure that there's no choice at this point but pull the cover and have a look. It's probably a leaking seal but I'm hoping for a weeping fill plug.

 

I use Royal Purple 75w-90 gear oil in both my differentials. It has friction modifiers.

 

I saw that at Autozone as well. In addition to the friction modifiers, I thought it's viscosity was too high....but maybe I'm just thinking of Redline.

Anyways, I bit the bullet and went with the Chevron Delo fluid. I'll keep ya'll updated how well that works out.

Look like a bad rear pinion seal.

Yep, I've slowly come to terms with the fact that I'm going to have to replace this seal. Is this going to be a pain in the rear? Of course. Would I rather do it here in Arizona than next month in the freezing cold? Heck yes! So I guess that's my answer. Do it right the first time while I have the chance. With a half dozen Harbor Freight, Autozone, and Napa stores within a ten-mile radius there no better time than the present.

First question: how do I tell what size the rear axle is? Since this is an ESV and everything that I've replaced so far has been bigger and beefier than usual, I'm assuming that I have a 9.75 inch axle, but I'm not 100% sure. Is there an easy way of determining this? Size, RPO code, etc?

Second question: What is the best way to remove the yoke? What kind of "pullers" will work?

Third question: Any advice or gotcha's?

The job itself is pretty self-explanatory and straight forward, but since this is my first time doing something like that I'm a bit unfamiliar with the concept of a crush washer/sleeve. I've done axle seals/bearings on my Dodge Ram once upon a time, but I've never had to do a pinion seal before.

 

I use ACDELCO here it is if you have amazon prime it should be fast ACDelco 10-4016 75W-90 Synthetic Axle Gear Oil - 32 oz

 

I use AC Delco in my Silverado...going to try AMSOIL here with the next fill though, see how that works.

 

Thanks for the tip; that's definitely important to know BEFORE you take it apart, eh?

One thing that I'm seeing conflicted information on, is whether to use grease or sealant (RTV sealant?) on the outside of the new seal before inserting it.

Also, I think this definitely calls for an impact wrench for once. I don't think my 4 gallon compressor delivering 2.5 CFM @ 90 PSI is going to cut it, so I'm probably going to have to go with an electric. Still, it's cheaper than labor.

I think I might tackle this tonight.

 

Thanks for the tip; that's definitely important to know BEFORE you take it apart, eh?

One thing that I'm seeing conflicted information on, is whether to use grease or sealant (RTV sealant?) on the outside of the new seal before inserting it.

Also, I think this definitely calls for an impact wrench for once. I don't think my 4 gallon compressor delivering 2.5 CFM @ 90 PSI is going to cut it, so I'm probably going to have to go with an electric. Still, it's cheaper than labor.

I think I might tackle this tonight.

I used some red grease on the inside of the seal that rubs against the yoke. However, i did use RTV(gray gear oil resistant type) on the pinon shaft splines to prevent leaks from behind the pinion bolt.

I used a Makita compressor with a similar rating(3.3 CFM) to easily break the pinon nut loose. The impact I used is an Astro Nano 1/2in with 450ft/lbs and it worked just fine. I do need a larger impact to break some of these rusted bolts in the Caddy like exhaust bolts, but the Nano works just fine and is very small for tight areas.

 

Front diff was AC Delco. Rear diff I went with the Advance Auto brand (Car Quest?)

 

Duplicate post

 

It is finished.

Overall, I got the pinion seal done in about 3 hours and it was really pretty easy. However, pulling the differential cover and getting it all cleaned up and in place with a new gasket was another matter altogether.

Despite the evidence of a leak, there was a crap-ton of fluid in there. I put about 2.5 qts in there which brought it up to about 1/2 inch under the fill hole. However, not only did I get about 2.5 qts out, but I also spilled about a quart on the driveway because I forgot to the drain it first! I'd like to say that I was excited to use my new impact wrench, but in reality I was in a hurry to pull the old seal out and verify that it was the same size as the replacement before Napa closed, just in case I needed to swap it for a different one. In my defense, I thought that most of the fluid was cooked onto the exterior of the differential, I was really surprised that it was so full. And it had a greenish tinge to it; almost like a little antifreeze was mixed in. Has anybody seen that before?

I'll probably recheck the fluid levels of both the front and rear this coming Friday, when I give it it's final oil change before hitting the road, just to make sure it's where it should be.

One thing that I did though, was to make a seal-driver out of the old seal. To do this, I cut away the protruding rubber on the interior of the old seal, and then flushed it up to the new seal (flat-surface to flat-surface) before knocking it home with a hammer. Perfect size, all force evenly distributed, no fuss.