Axle seal question

[reaper01]

Hi, I have a 1991 m923a2 and the other day I noticed some oil on the front rear axle, I've figured out that it's leaking from the drive shaft thata between the two rear axles. My question is what is the part number for that seal/gasket and how big of a pain in the butt is it going to be to change it out. Thanks.
Cole.

 

[74M35A2]

An easier fix may be to openly vent all 3 of your axles to the atmosphere. I did, and my pinion flange leaks immediately stopped. The factory vents in these axles allows a small amount of pressure to be built up before opening. That can push oil past seals that are getting tired. Few threads here about doing so.

 

[Floridianson]

You can just call Memphis Equipment and they will hook you up. The big problem is the nut that holds on the pinion. Big bar might get it off and I had to use my one inch tire impact to get it right back to where it was so cotter pin would line up. Good luck.

 

[74M35A2]

If the pinion flange nut is too tight, you can put a socket and breaker bar on it and wedge the handle into the frame rail. Then, drive the truck forward or backward a few feet, depending upon which was fhe nut needs fo dofate to loosen.

I did fhis move on a GMC C7500 medium duty truck transmission, and it worked perfectly.

 

[Floridianson]

Sounds scary to me. Right tools right know how.

 

[Tow4]

I have done this in the past. It's not hard.

Replacing the pinion seal is not that hard. I got my seals from bigmikem35a2 on Ebay for $15.95 each. I would buy a couple because if one is bad the others are probably not far behind. I have replaced 2 on my M818.

Read the TM first. I suggest using a 3/4 inch impact to remove and re-install the pinion nut. Use PB Blaster or WD40 if you have a hard time getting the pinion nut off.

The process is as follows:

Remove drive shaft if the flange the seal is leaking at is driven. Make a reference mark on the pinion flange and drive shaft flange so they get back together the same way.

Remove the cotter pin from the pinion nut. You need to be able to tighten the nut back to the same torque so make reference marks on all parts. Take a magic marker and draw a line across the pinion to show where the cotter pin is. Mark the pinion nut on the ears on each side where the cotter pin was on the nut, also mark the pinion flange.

Remove the pinion flange nut. The pinion flange should now just pull off. Check the pinion flange seal surface and make sure it is smooth. One of mine had some scratches that I had to sand out with some 1000 grit paper and buffing compound. If there is a lot of scoring you can have a new sleeve installed on the flange.

Remove the cover that has the seal and remove the seal. Clean the mating surfaces where the seal goes and where the cover mounts to the differential. Clean the mounting surface on the differential.

Put a bead of RTV where the seal goes and install the new seal. Check to make sure RTV has not gotten on the front of the seal; wipe it off if necessary. Apply a bead of RTV around the cover mounting holes. Re-install the cover on the differential.

Put a little grease on the seal lips and noting your alignment marks re-install the pinion flange. Re-install the nut and torque it down until the marks line up with the marks on the pinion. Re-install the cotter pin. Re-install the drive shaft if applicable.

Check the oil level and you are done.

 

[silverstate55]

To complement ray's post above:

I recently changed all 4 pinion seals on both rear axles & the front & rear seals on the transfer case on my M931A2...the seals are all the same part number.

The axle pinion nuts require a 2-1/4" (2.25") socket once you remove the cotter pin, and I was able to use my 3/4" impact wrench to remove & re-install these...some quick taps on the trigger got the cotter pin holes aligned with no difficulties, other than finding the appropriate size of cotter pin. Seems that all the ones local to me were too large of a diameter at that length to cleanly fit into the hole, so I had to do a little judicious filing to get them to slide in.

The transfer case lock nuts use a 1-5/8" socket (1.625"), and the torque on these is pretty significant. I had to use my 1" impact wrench at maximum air pressure to get these off. The hardest part was removing the parking brake assembly, but overall it wasn't that bad...and it made cleaning the oil out of the parking brake assembly far easier once removed.

I used my axle seal driver to seat them all: a length of ABS pipe with couplers made for Deuce inner axle seal seating, and it fit perfectly on these seals for a nice clean install. I did coat the inner part of the seals (where they fit over the pinion and/or output shafts) with silicone grease to make sure that they weren't a dry fit.

Some of the bolts holding the driveshafts to the input pinion yokes were actually stripped, so I replaced them all...each coupling uses 8 bolts & nuts, so I ended up replacing a total of 48. I believe that they are Grade-8 5/16" Fine Thread, and I use Loctite on each one to ensure that they stay in place.

So far, so good....

 

[Floridianson]

What TM had the torque specs for the pinion nut? http://www.harborfreight.com/3-4-quarter-inch-heavy-duty-impact-wrench-66984.html.

 

[silverstate55]

What TM had the torque specs for the pinion nut? http://www.harborfreight.com/3-4-quarter-inch-heavy-duty-impact-wrench-66984.html.

I found it in TM 9-2320-272-24-3, page 4-576. 300-400 lb-ft.

 

[Floridianson]

Yea the HF one would take care of that. Thanks