Oil Leek at highway speeds

I recently bought a bobbed Deuce. I drove it three hours home and ended up developing a rear main seal leek. I driving just under read line doing 50-54. When I would stop and drive around a parking lot it would stop. I tried driving a little slower at around 2k and still had the rear main leaking. It was leaking enough that my clutch started slipping as I got close to my shop. I was able to spray brake cleaner up on the clutch and flywheel through the bottom hole enough to get the clutch to stop slipping. Now I drive it around 1.5k and it dose not leek much. I have a few small leaks on the drive side but nothing major.
We have another deuce and it does not have that problem and I talked to a friend of mine whom has one and he does not have the problem either. I am going to check to see if the breather is plugged. the motor have 6k miles and 400hr. It runs cleaner and better than our other truck. Anyone else have this problem? Is there a way to fix it?

Thanks

An oil leek? Is that some kind of onion?

The only way to stop a rear main seal leak is pull the transmission and replace it.

Did you smell the oil? Sounds alot like a trans issue many of us have had. If it smells like gear oil, drain some fluid out of the trans. I ended up draining 20oz(Mt.dew bottle) out of mine and it worked like a champ. If you look at the way the flywheel is designed, it is very hard for motor oil to leak and get on the clutch.

For the moment, don't condemn the rear main seal.
Check the leaking fluid carefully for possibly being transmission oil. Check the transmission oil level. Consider updating the transmission oil to a 50W gl1. Check the transmission fluid vent for proper function.
If none of t hat nails it, carry on worrying about the rear main seal.
Make sure the plug at the bottom of the bell housing is removed in either case. It should only be there for fording purposes. With it removed, the oil (from either side) should not spoil the clutch so easily.

Jake0147 said:

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Make sure the plug at the bottom of the bell housing is removed in either case. It should only be there for fording purposes. With it removed, the oil (from either side) should not spoil the clutch so easily.

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Well..., it does happen! Read here: http://www.steelsoldiers.com/deuce/41660-oil-overfill-possible-rear-seal-leak.html

G.

Mine was doing the same thing. I had overfilled the engine oil when i changed it.i had the plug out of the bellhousing and is was still making the clutch slip once oil level was correct no more oil leak. Oil level is very critical on these trucks as they build alot of heat and the oil expands to the point of causing leaks.so first thing you do should be make sure the trans fuild is about 1 inch below the fill hole cold. and engine oil is 1-1.5inches above the full make totally cold.you can check them hot but unless you drive it around fully loaded you wont get it up to full op tem and most likely over fill them.

The guy I bought the truck from owns his own diesel service shop and I also have a shop and work on diesels. I did check the oil before we left and it read to the full mark. I have not checked the trans fluid level but it is definately oil that was leaking. I have been driving it for a few days not butting on 100 miles or so. It has not really leaked much of anything since I have not been driving it over 2k. I would think if the seal was bad it would leak all the time. The guy I bought it from said he thought it was because it was building up to much crank case pressure at higher Rpm's.

You are correct. The high rpms leak means that it is probably the trans.

So the trans. level is supposed to be 1" BELOW the fill plug hole?

If you put your finger into the filler hole, with your first knuckle through the hole, and your finger tip bent downward, it should just touch the oil... So it should be more like 1/2 inch below the threads on the filler plug's hole.

There is a lot of argument about what the level should really be. The Army says 1/2 inch down, but tons of experience with other Spicer transmissions says fill until it spills out of the filler plug's hole.

One thing to note: the input shaft doesn't have a rubber wiper seal. It relies mostly on the clearance between the input shaft and an input sleeve, the fact that the input shaft is pretty far above the transmission's static oil level, and the input gear's ability to fling most of the oil away from the input shaft bearing and sleeve. However, there are 4 cap screws, and a gasket, that hold the input sleeve to the front of the transmission, and if they happen to leak, you will get more seepage than you want. I have a feeling that this potential for a leak is the reason the Army recommends a lower oil level.... That and the truck could be parked on a 45 degree hill front down.

-Chuck

Thanks for the thorough description, Chuck.

I'm with you in that all my past experiences with Jeeps and such (and even my air cooled VW transaxles) have been "to the bottom of the fill hole".
But I can see the military wanting a little "extra insurance" for parking on a steep downhill.

My truck is always parked on nearly perfectly flat ground so no worries there.

Have you considered that maybe one of your pistons is getting excessive blow-by which builds up crankcase pressure at high rpm? It could be as easy as a pcv valve (if these engines even have such a thing).

Unforgiven said:

Have you considered that maybe one of your pistons is getting excessive blow-by which builds up crankcase pressure at high rpm? It could be as easy as a pcv valve (if these engines even have such a thing).

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They all have a 1 inch, or so, rubber slobber hose that vents the valve cover.

-Chuck

It is not trans fluid it is engine oil. When I take if for a ride today I will see what kind of flow I am getting out of the breather. This motor seams to run better than our other one and it also smokes less when when you drive it. The oil pressure gauge reads lower than the other one I think. The gauge has thirty at 12 o'clock. At idle it is at the first line and running down the road it gets to the the middle of nothing and 30 lbs.

Ok, if I am understanding you, your engine probably has excessively worn main bearings. Oil seals won't work if there is significant main bearing slop. You should have between 15 and 30psi oil pressure at idle, and about 60psi when the engine is going 2500 rpm.

This is a common problem. Because the MF engine drains all of the oil out of its filter canisters overnight, when you start a cold MF engine it runs without oil pressure for 12 to 15 seconds. During that time, it is pumping air through (and blowing the oil out of) all of the pressure fed bearings... not a good thing.

MF Engine bearing longevity can certainly be improved by replacing the stock cartridge oil filters with one of the many spin-on oil filter adapter plates... assuming you use spin-on filters with anti back-flow valves built in.

A couple of SS members make these adapter plates, Jatonka and Wesfolk come to mind.

-Chuck

I plan on getting the anti drain back filters for both my trucks. I try not to turn them off unless I have to. It makes me cringe how long it takes for the pressure to build. I am going to hook up a oil pressure tester I have at my shop to it and just make sure those readings or correct. If it is the case that it has that low of oil pressure I will just run her till she dies. It does not miss a beat and pulls better than our other one.
I also checked the breather and had stuff coming out of it. Barley anything at start up and after driving it for 30 min or so just enough was coming out that you could see it. I think my cummins 5.9 motor I had in one of my trucks had more coming out of the breather.

I hooked up a manual gauge the other day and I had 70 psi on immediate startup and 50 psi at a very low idle. So the problem is just the gauge. So I have a manual one on the way. So I the seal just tired and can't take the rpm? I have been driving it under 2k and have had no leaks out the back.

Murdawg said:

I hooked up a manual gauge the other day and I had 70 psi on immediate startup and 50 psi at a very low idle. So the problem is just the gauge. So I have a manual one on the way. So I the seal just tired and can't take the rpm? I have been driving it under 2k and have had no leaks out the back.

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That's wonderful news. Sounds like your bearings are in good shape.

If the engine sat unused for a long time, the seal surface could have some rust that gobbled up the seal, or the seal could have hardened and just broke. I would bet on the latter.

-Chuck