Axle vent tube gear oil coming out

[Keith Knight]

I have a 2003 M1078. Purchased it September 2015 it had ALL the drain plugs remove and no fluids. Properly filled everything 6 years ago. I’ve driven it 5,000 miles in the past 6 years the longest trip was 3 hours of straight driving. Yesterday I drive it 15 miles and when I parked it there was 4” diameter gear oil spot under the real axle, a quick inspection and it’s coming out of the vent tube!!!!! Checked the oil level and it’s perfectly at the bottom of the fill plug. The front and rear axle were the same temperature. I don’t have any other axle leaks. The oil look like I just put it in there.

What the heck would suddenly cause it?

 

[Mullaney]

I have a 2003 M1078. Purchased it September 2015 it had ALL the drain plugs remove and no fluids. Properly filled everything 6 years ago. I’ve driven it 5,000 miles in the past 6 years the longest trip was 3 hours of straight driving. Yesterday I drive it 15 miles and when I parked it there was 4” diameter gear oil spot under the real axle, a quick inspection and it’s coming out of the vent tube!!!!! Checked the oil level and it’s perfectly at the bottom of the fill plug. The front and rear axle were the same temperature. I don’t have any other axle leaks. The oil look like I just put it in there.

What the heck would suddenly cause it?

.
Dirt Daubers or maybe Spiders?
Something restricting the vent tube?
Maybe even a kink in your vent line?

Based on what you described, it has to be something like that. Normally the gearboxes breathe as they get warm. Something had to have been restricting the air - then when it wasn't breathing - you saw the results.

 

[Keith Knight]

I completely agree with you but no kink and the vent has that little metal cap on it preventing critters from getting into it. But I’m going to have to pull it all apart and check everything.

 

[NDT]

Maybe a CTIS seal leak is pressurizing the axle. Paint some Mr Bubble/water solution on the vent hose and and see if air is coming out.

 

[ToddJK]

Sometimes those caps get dusty, just enough so the axle/diff can't breath.

 

[simp5782]

I have a 2003 M1078. Purchased it September 2015 it had ALL the drain plugs remove and no fluids. Properly filled everything 6 years ago. I’ve driven it 5,000 miles in the past 6 years the longest trip was 3 hours of straight driving. Yesterday I drive it 15 miles and when I parked it there was 4” diameter gear oil spot under the real axle, a quick inspection and it’s coming out of the vent tube!!!!! Checked the oil level and it’s perfectly at the bottom of the fill plug. The front and rear axle were the same temperature. I don’t have any other axle leaks. The oil look like I just put it in there.

What the heck would suddenly cause it?

Turn the ctis off and see if it still does it. CTIS pressure from a bad seal could be pushing it out.

 

[Keith Knight]

Very Interesting thought. I’ll definitely do that.

 

[Keith Knight]

Pulled the vent line off and it’s clear. Cleaned the remaining gear oil out of it.
I’m unable to check the CTIS theory currently because I have it parked in an air conditioned shop prepping it for painting the interior of the habitat. I’ll have to check that on Sunday when I pull it out of the shop.

 

[Keith Knight]

Back to this old problem.....
So back in September of 2021 I did the soapy water at the rear axle vent area and cycled the CTIS and no bubbles. So never found any cause of this problem and moved on. Well after 3,500 mile trip it's obvious it's still occurring occasionally. I just did another soapy water test and cycled the CTIS and still no bubbles.
My only conclusion is that the vent line has a U shape to the line, kind of like a P trap on a sink and SOME HOW...... a small amount of the gear oil is getting slung up off of the axle shaft and getting into the vent line settling down int the P trap then when enough oil gets into it and blocks the air flow when the axle heats up and then the hot air trying to escape pushes the oil out the vent, clears the line then then starts the slow process over again. Any one else with this problem and did you find a solution? I'm going to go look to see if can re shape the hose so that any gear oil that would get in the line would drain back into the axle and prevent any accumulation of the gear oil.

 

[coachgeo]

Back to this old problem.....
So back in September of 2021 I did the soapy water at the rear axle vent area and cycled the CTIS and no bubbles. So never found any cause of this problem and moved on. Well after 3,500 mile trip it's obvious it's still occurring occasionally. I just did another soapy water test and cycled the CTIS and still no bubbles.
My only conclusion is that the vent line has a U shape to the line, kind of like a P trap on a sink and SOME HOW...... a small amount of the gear oil is getting slung up off of the axle shaft and getting into the vent line settling down int the P trap then when enough oil gets into it and blocks the air flow when the axle heats up and then the hot air trying to escape pushes the oil out the vent, clears the line then then starts the slow process over again. Any one else with this problem and did you find a solution? I'm going to go look to see if can re shape the hose so that any gear oil that would get in the line would drain back into the axle and prevent any accumulation of the gear oil.

maybe remove vent cap, put a hose on it and run it over to a removable tiny bottle (or one with drain) to act as a catch can. Then hose up to high spot; off the top of the bottle, to be "the vent"? Bottle could even be a fat clear hose maybe? Clear will make it easy to check on when to empty it back into the pumpkin.

Not a FIX but will keep it cleaner down there. Granted..... might be an advantage to keep the "automatic anti rust prevention device" you seem to have gotten installed on your axle.

 

[GeneralDisorder]

The CTIS seals rotate on the spindle and simply cycling the CTIS while stationary is not a sufficient test.

Pull the banjo bolts for the CTIS valve off the wheel stud and smell for gear oil.

Have you done a wheel bearing service? The inner wheel bearings are supposed to be repacked, torqued, and the hub and CTIS seals replaced as well as the reduction hubs properly shimmed - the military does this annually which is probably overkill but at least every 5 years this should be performed.

If the axle is not overfilled or generating a ton of heat then pretty much the only other possibility is the CTIS system.

 

[Keith Knight]

maybe remove vent cap, put a hose on it and run it over to a removable tiny bottle (or one with drain) to act as a catch can. Then hose up to high spot; off the top of the bottle, to be "the vent"? Bottle could even be a fat clear hose maybe? Clear will make it easy to check on when to empty it back into the pumpkin.

Not a FIX but will keep it cleaner down there. Granted..... might be an advantage to keep the "automatic anti rust prevention device" you seem to have gotten installed on your axle.

, That’s not a bad idea.

 

[Keith Knight]

The CTIS seals rotate on the spindle and simply cycling the CTIS while stationary is not a sufficient test.

Pull the banjo bolts for the CTIS valve off the wheel stud and smell for gear oil.

Have you done a wheel bearing service? The inner wheel bearings are supposed to be repacked, torqued, and the hub and CTIS seals replaced as well as the reduction hubs properly shimmed - the military does this annually which is probably overkill but at least every 5 years this should be performed.

If the axle is not overfilled or generating a ton of heat then pretty much the only other possibility is the CTIS system.

I definitely have not did all of that PM work sounds expensive and extremely extensive for annual PMs. I thought the rear axle had wet bearings. I have to give all that a thought. And in the meantime I’ll do the sniff test.

 

[Ronmar]

I definitely have not did all of that PM work sounds expensive and extremely extensive for annual PMs. I thought the rear axle had wet bearings. I have to give all that a thought. And in the meantime I’ll do the sniff test.

The sniff test may or may not be conclusive, as if the axle vent is not leaking CTIS air when stationary, it may not be bad enough to allow gear oil into the CTIS side of the seal as the axle side, being vented, is never under any real pressure...

The outer bearing is wet, the inner bearing is grease packed, as it is 2 CTIS seals away from the wet side… If you are still getting oil out of the axle vent, you can also simply unplug the CTIS controller and see if it stops spitting oil out the vent when you drive.

 

[Keith Knight]

I’ve been keeping it unplugged until I need to air down or up and recently installed a switch to do this. And honestly only needed to do that maybe four different times in the last 3,500 miles. So I’m leaning more to my earlier theory and may just try to implement the earlier suggestion and put a catch container on it. Any one seen a good video on repacking the bearings and replacing the seals? Also any good place to purchase the seals?
Maybe something like this and remove the filter.

 

[GeneralDisorder]

The usual surplus suspects for the seals and shim kit. To properly torque the spindle nut you need a rather oddball socket - 3-7/8" Eight Point extra deep - that really isn't available to buy since it's made special for the military by OTC......

5120-01-567-9296 3-7/8" Socket 3114485C1 OTC 1913GOV 521687 ⋆ DP Equipment LLC

FMTV Hub Socket 5120-01-567-9296, 3-7/8″ Socket, Navistar 3114485C1 OTC 1913GOV SPX 521687 Deep version of OTC 1913 R3B2

dpequip.net

But you can make your own by getting the civilian version and cutting it then extending it with a section of pipe. But also the torque is really low and not particularly precise (10 to 20 ft/lbs) so if you are used to packing bearings and what that kinda feels like you can accomplish the task with just a screwdriver and a few calibrated taps of the hammer on the roll pins attached to the nut.

On my truck (2008 A1R with 2,045 miles by the military and about 4x that in surplus) the grease was disgusting, the inner hub seals had failed and let in water, and the (likely one time) that PVT Snuffy did a hub service three of the four I could remove the spindle nut by hand (not torqued). Also one of my inner CTIS seals I found had been torn by the spindle threads on installation - which apparently is common because the hub is heavy and soldiers that really shouldn't be attempting it on their own will set the hub on the spindle during installation and damage the seal.

If you have had your truck for that long and have not done this service then it should be at the top of your list. These are not fire and forget axles - they have a lot of foolishness going on and the longevity of the reductions drives depends on accurate shimming, the seals (especially the inner "live" seal that keeps water out of the inner bearing) need to be replaced to keep the gear oil, grease, and pressurized air from mixing - also the condition of the air system and especially the dryer/filter play a role in the longevity of the CTIS seals as they are directly exposed to moisture, rust, etc from the air system.

 

[Keith Knight]

Thanks for the heads up before I start diving into that project!!! I’m surprised I have seen more of this subject here in steel soldiers. Or maybe it’s like listening to my wife I just ignored it!