Hi all,

I thought I'd report on my replacement of the left front output bearing and seal. Starting this spring I had noticed what I had thought was left-over grease covering the upper face of the lower control arm. However I guessed it was actually oil leaking from the front differential. When I checked the level, sure enough it was down a bit. So I decided to look into changing out the seal. After some searching, which was not easy, I did find some references and examples of similar work being done (also on a Safari van). What I realized was that I might as well replace the bearing while I was at it and instead of replacing the seal, I'd get a new cover with the seal already mounted.

Like a lot of things on our Blazers, much of the effort is just getting to the part. In this case you have to remove the left front drive axle. Now although some say it is possible to remove the axle without taking off the steering knuckle, for this job you will want to take it out so you can easily get at the axle and differential cover.

Parts/Tools Used:

• GM 26053326 - "Output Shaft Bearing"
• GM 12471587 - "Carrier Cover"; i.e. left differential cover with seal
• Permatex Anaerobic Flange Sealant pn 51531 - equivalent to GM 1052357 per pg 81 of 2015 Permatex Master Parts Catalog
• 3 Jaw Pilot Bearing Puller - modified for small internal clearances, from eBay
• New front drive axle oil, 80W-90
• Set of crow foot socket heads to get at bolts behind truck frame at top of cover.

Drive axle partially removed before I realized I would have to also remove the steering knuckle to get it out.


Close up of left side of differential with axle removed looking into the differential

To start you will want to drain the the oil out of the front drive axle. This is a good opportunity to change it. It is easier to refill with a pump.

To remove the cover plate, I found that the upper two cover bolts cannot be reached with a socket. I could have removed them with a combination wrench but I took the opportunity to get a set of metric crowfoot wrench heads for my socket set. This made cracking the top nuts much easier and later allowed me to actually use a torque wrench on them when I installed the new cover. These bolts have 13 mm heads.

With the cover off, next was to remove the bearing.

A few things to note about the bearing removal and replacement:

• The bearing is installed with the flat face that has the stamped letters facing outward. The rounded face of the bearing faces into the differential.
• To get the removal tool to work, I had to cut the tips off of the jaws. After I removed the bearing I realized I should have also cut an angle in what would be the outside facing parts.
• The outer face of the bearing is installed flush with the surface of the carrier bearing adjuster. There is no lip to stop the output bearing from being pushed in too far.
• You do NOT want to mess with the bearing adjuster: the thing with the teeth and the locking mechanism.
• I used a bearing insertion tool that guided it in. When I got close to it being completely in, I removed the head of the tool and replaced it with a larger one that I installed backwards so that it only had a flat face. With the flat face I was ensured of not over inserting the bearing.

Outer face of bearing showing stamped lettering. This must be installed with this face facing outward.



Inside face of new cover.


Outside face of new cover.

Bearing removal tool before modification.


Bearing removal tool mounted in place and pulling commenced.


Modified jaws of bearing puller showing that in addition to shortening them, I should have filed down the parts that extended outward.


New bearing installed. I pre-oiled it as a precaution.


Bearing insertion tool. When it was close to being fully in, I took one of the larger anvil heads and mounted it so only the flat face was outward so that for the final taps of the hammer I would not over insert it.


New cover installed. I used the Permatex flange sealant. I also cleaned the surfaces with brake cleaner to ensure a good seal. The original cover did not have any sealant but this sealant was called for in the GM manual in the steps for rebuilding the front differential and axle.

I'm leaving the differential empty of oil for at least a day to ensure it is cured. According to the Technical Data Sheet for the sealant, the part can be returned to service after an hour with no need to only partially tighten and then re-tighten (like with RTV) with tightening to full torque (18 ft-lbs) during assembly.

UPDATE 2019-06-03:

• Be sure to use plenty of the sealant on the cover plate as the rubber on the inside of the plate is not sufficient to seal on its own.
• With the drive axle out, it is a good time to replace the CV axle boots and refresh the grease in the CV joints.
• Replacing the bearing might or might not be absolutely necessary but if the seal failed because the bearing was no longer centering the axle shaft, then all this work would have to be repeated.
• If you are replacing the CV axle, be warned that many aftermarket shafts seem to have a tight fit back into the differential.
• It is possible to get a new seal for the cover and replace the old one in the original cover. The seal is of a standard size and the markings on it can be used to find a replacement. I obviously went with replacing the whole plate since the total cost was not too much.
  
  Close up of new axle bearing seal with identification markings.

Edit: Added GM Service Manual excerpts for this repair.

 

 

Thanks. I thought I might as well share in case anyone else is faced with the same repair.

 

Good stuff! Thanks for posting all that, I'm doing this same repair soon. One question, what should the torque be for the cover bolts? TIA

 

Thanks. The torque for the cover plate bolts is 18 ft-lbs. I'm attaching an excerpt from my manual that helped (and also includes the torque specs.)

 

I looked for both the seal and the cover, cannot find either.

For myself anyway, this leak has rendered my truck requiring a used front differential because the correct seals cannot be purchased

I contacted GM service parts and operations and requested the part to have a build order created, but was denied and, no dealers have it as far as I could see

 

Could you not use the information in the pictures above to find a replacement axle grease seal? That sucks!!

I did a quick Google search for AAM 40007630 for the axle seal and got a few hits including this one: https://cmgearworks.com/product/7-25...pair-7-25-ifs/

You'll want to double check if this is correct but I think it might be.

Good luck!

 

the part number I have for this part (seal alone) is GM 12471586, searching the new number which you provided I was able to find the same seal it appears!

7.25″ 4X4 Front Axle Seal Chevy S10 GMC S15 1997-2003

American Axle Manufacturing 40007630 (seal)
General Motors 12471586 (seal) 12471587 (cover and seal)

Only source currently for cover and seal:

https://www.alibaba.com/product-deta...12275d45pTAw2E

 

I'm glad it worked.

And thanks for posting the link. I'm sure others will find it useful.