How-to: fixing a leaky outside axle seal

[FormerNewMVGuy]

There is a cork insert in the keyway just behind the outer seal. when this cork fails the gear lube runs through the hub and down the inside wheel, Now while this is happening, it is washing all the grease out of your wheel bearings. So dont drive it till you fix it!! Some guys just use rtv silicone. I bought some rubberized cork and cut it to fit the keyway, Then i put a little dab of silicone on it before i install the outer seal, Havent had any leaks sense!

 

[AceHigh]

I was checking the front axle vent this week and it was not plugged up- it was GONE! Just a hole there. Who has them?

Great write up- thanks!

 

[FormerNewMVGuy]

I think you can get them at Napa. Just take one out of the rear and take it along so they can match it up.

 

[jesse poundstone]

I didnt think there was supposed to be any gear lube in the hub arent they grease packed bearings or is that the seal just behind the spindle nut, and there is only gear lube out at the very end of the spindle? im am a truck mechanic all drive axles i have fixed have gear lubed wheel bearings not grease and the only seal is at the hub but i guess the military wanted to keep the lube compartments separated as much as possible can any one enlighten my thoughts?

 

[cattlerepairman]

I didnt think there was supposed to be any gear lube in the hub arent they grease packed bearings or is that the seal just behind the spindle nut, and there is only gear lube out at the very end of the spindle? im am a truck mechanic all drive axles i have fixed have gear lubed wheel bearings not grease and the only seal is at the hub but i guess the military wanted to keep the lube compartments separated as much as possible can any one enlighten my thoughts?

You are correct; the military wanted to completely separate the outer end of the drive shaft (oil lubed via hollow axle) from the hub that contains the wheel bearings. There is a cool graphic floating around (I think Gringeltaube made it) showing the cross-section. I am not an engineer and can only speculate why the military wanted greased bearings instead of oil-lubed.

Failure mode is therefore usually a failing keyway cork (I guess a failing outer seal is somewhat rarer) that allows gear oil to enter the hub from where the driveshaft flange sits, thus washing the grease out of the bearings (forming blobs of oily grease in the hub). The inner seal, being grease-tight but quite apparently not oil tight, allows the oily sludge to pass into the brake drum. The brakes remain ok as long as the oil slingers fling the goop away from the brake shoes and the drain holes in the drum are not clogged.
Once you see the gooey mess run down the inner flank of the inner dual, your brakes are well oiled, I guess.

Consensus seems to be that oil on the bearings is pending desaster; on the other hand, units have been known to deliberately leave out the keyway cork and allow oil to get to the bearings. The argument is that the set-up is not designed to supply enough oil to the bearings, so they will be under-lubed.

I am not convinced that bearings that were well greased but then get immersed in gear oil due to a failed seal will really automatically die a quick death. On the 12 bearings I got to look at very recently, there was plenty of lubricating goop (oil and grease). While probably not the ideal and designed lubricant, I do think that they are lubed enough at the rpms and temps they see to make them survive and last for a while. All this is meant to say is that I'd not panic about it, that's all.

 

[dcwilkie]

Dang- all I did was unbolt, slide the axle out, clean everything, RTV the new paper gasket both sides, slide it over the axle (axle was lightly greased), slide everything back in and bolted down using new split washers. I didn't jack up ANYthing. Was this wrong?

 

[rmgill]

Could be you were on a surface that allowed the windup to be relieved. Soil and gravel allows this.

 

[Snarky]

Oil is not a solvent it's not going to wash you grease away. If it was properly greased before it'll remain greased with oil around it. I might give it a dab of grease when I checked the brakes, but really guys, that cork key way stopper is useless, sooner or later it'll leak and I'm sure the majority of trucks have oil in the hubs.

I had some things to add: You can cut a new paper gasket using paper from a magazine, someone here mentioned that, I tried it, it works. The cork create a gasket material is useless here I think the best best would probably be the rubber sheets pipe fitters use, but I haven't tried it.

You should clean the surfaces you apply silicone to, and after you apply it you should let it set up for about 5 minutes before putting your axle back on. This will prevent future leaks.

Thick impact sockets are your friend, chrome doesn't really cut it in this application. A 1/2" impact gun is also you friend, unless someone was watching them, I don't think anyone in the military would actually set the torque on those particular bolts.

 

[dcwilkie]

Nope

Could be you were on a surface that allowed the windup to be relieved. Soil and gravel allows this.

I was on concrete. Hmmmmmmm.........

 

[dannyd2450]

Maddawg, Im not the most technical guy (i am a desk and computer guy)... but with this post, I replaced the cracked gasket in no more than 30 minutes!!! Thanks for outlining the project, educating the newbies like myself, saving me a crapload of money, and saving more time that can be left for beer!

 

[TMNT]

I was on concrete. Hmmmmmmm.........

You didn't hurt anything if it slipped back together with no problems. It just means you got lucky and the splines lined up. I found it much easier to just jack the whole axle up from the differential so that both sides are off of the ground (per the TM). I never had any problem getting the axle shafts back in and lined up.

 

[TMNT]

Oil is not a solvent it's not going to wash you grease away. If it was properly greased before it'll remain greased with oil around it. I might give it a dab of grease when I checked the brakes, but really guys, that cork key way stopper is useless, sooner or later it'll leak and I'm sure the majority of trucks have oil in the hubs.

I had some things to add: You can cut a new paper gasket using paper from a magazine, someone here mentioned that, I tried it, it works. The cork create a gasket material is useless here I think the best best would probably be the rubber sheets pipe fitters use, but I haven't tried it.

You should clean the surfaces you apply silicone to, and after you apply it you should let it set up for about 5 minutes before putting your axle back on. This will prevent future leaks.

Thick impact sockets are your friend, chrome doesn't really cut it in this application. A 1/2" impact gun is also you friend, unless someone was watching them, I don't think anyone in the military would actually set the torque on those particular bolts.

The gear lube will absolutely wash the bearings out clean if/when the keyway fails. I've experienced it numerous times. That being said, I drove many miles with that condition with no harm to the bearings or races. Gear lube in the hubs will almost certainly result in gear lube going past the inner seal and getting slung out of the drum onto the inside of the wheel and tire. The inner seal doesn't seal well enough to stop the liquefied combination of gear lube and bearing grease. Believe me, it makes quite a mess.

Post #248 shows what it looks like when the gear lube gets into the hub and washes out the bearing grease: (I can't figure how to link to that specific post here.)
http://www.steelsoldiers.com/showth...ka-Big-Betty&p=1399224&viewfull=1#post1399224

Checking and servicing the hubs is one of those tasks that can be done in a day (with practice and the right tools) and it should be done after every encounter with deep water or mud. Its a great opportunity to clean, check, and adjust everything at the wheels.