M998 Front Differential

[General Hood]

The other day I noticed oil on my left front brake rotor, and got under the truck to inspect ( thinking I had a brake caliper leaking) but it turned the leak was coming from the differential side of the brake rotor. I unbolted the half shaft from the differential flange and oil poured out. Okay, looks like I need to replace the output seal on the differential. Upon further inspection, some knucklehead in the life of this truck had rounded off the brake line connector to the caliper. GRrrrr
Got the caliber out of the way so I could remove the output shaft flange and the entire nut and surrounding area was heavily coated in silicone. I dug at it with a slotted screwdriver and box blade for a good while in order to expose the nut. Here is an image after I dug and scraped silicone for half an hour

Any helpful tips on the seal removal / replacement would be appreciated. After seeing the workmanship of previous MV mechanic , I proceed with caution

 

[cwc]

I have seen the silicone used before also, seems it must be a somewhat common practice. It is interesting that yours was leaking so much even with a lot of silicone. Maybe it was applied to oily parts and did not get a good deal.

I recently replaced the seals on the front of a M998. It has the older style differential brackets that have to come off to access the seal. The nuts are hard to get to; I used a socket that I had previously modified by grinding flats on the drive end, and held it with an open-end wrench, which made it fairly easy.



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[Action]

Ground off the brake line connector to the caliper?
Can you wiggle to output flange?

 

[NDT]

The seal that is leaking or missing is between the flange and spline. Pvt. Dope tried to shortcut the proper repair with a tube of silicone.

 

[jkcondrey]

The flange will just pull off, mine did. You may need a light slide hammer to break free. There should be a rubber washer, with grooves in it to match the threads on the shaft. It can be lightly coated with silicone to aide in sealing. Order that and the main seal. I don't recall what I paid, but the wife didn't notice so probably not much.

 

[Action]

I had asked if the flange wiggles, because it looks like the nut isnt down all the way. That will definitely cause leaks.

 

[General Hood]

I had asked if the flange wiggles, because it looks like the nut isnt down all the way. That will definitely cause leaks.

No wiggle, everything is tight. I drained the differential as well, oil looked good and no metal flakes or fibers stuck on the magnet. That's always a good sign

 

[86humv]

Star washer 5330-01-487-7129, p.n. 5939517.

 

[General Hood]

Star washer 5330-01-487-7129, p.n. 5939517.

Thanks Greg, washer and seal on order

 

[AOR]

I was going to say the same thing about the star washer. I don't think I have ever seen that much silicone under a flange before. I ordered new output seals and star washers and a pinion seal for mine then when I cleaned it off and took a better look it was only the pinion seal leaking and dripping off of the brake caliper bracket. I replaced the pinion seal only and have driven about 200 miles so far and no more oil

 

[Retiredwarhorses]

If when you pull a Halfshaft and you get 80-90GO between the HS and Rotor, it’s the stub axle flange seal Early version was just several o-rings stuffed in there, now it’s a specific seal. I still put a bead of rtv on the face of the nut when I install them as double protection.

 

[Ezraroot]

Does anyone know the year that they changed the bracket that causes you to remove the diff to repair this? I have the same problem and am about to tackle it this weekend.

 

[Action]

Does anyone know the year that they changed the bracket that causes you to remove the diff to repair this? I have the same problem and am about to tackle it this weekend.

Where is the oil on yours?

 

[dilvoy]

The early Humvees did not use the star seal on the splined shafts. They used two black O Rings. Not the best thing, but that is what AMG used.

 

[cwc]

Ezraroot, you should be able to see whether the bracket overlaps the seal without needing to take anything apart.


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[Ezraroot]

Where is the oil on yours?

This is the drivers side front.

 

[General Hood]

If when you pull a Halfshaft and you get 80-90GO between the HS and Rotor, it’s the stub axle flange seal Early version was just several o-rings stuffed in there, now it’s a specific seal. I still put a bead of rtv on the face of the nut when I install them as double protection.

As a note of interest, there were neither O Rings nor blue star washer on my unit once disassembled. I can only speculate the overdose of silicone was a quick fix field maintenance, and was never followed up by any proper maintenance procedure

 

[General Hood]

Back on the project- I decided to go ahead and do both sides while I was at it. The driver side that leaked had no O ring or seal, passenger side had a crushed O ring and 2 smaller versions of the replacement seal


Please confirm only one of the new blue seals replaces what I removed. I'd rather ask and beg forgiveness, than second guess myself on this

 

[86humv]

Use one each, and put together dry...swipe some good RTV sealant around star washer / axle spline then install & tighten nut.

 

[General Hood]

Use one each, and put together dry...swipe some good RTV sealant around star washer / axle spline then install & tighten nut.

Got it, thanks