Transmission Leak....

[mckeeranger]

I took the leaky deuce for a 20 mile drive yesterday after work. As soon as I stopped, I chocked the wheels, rolled under it and laid a bare hand on the transmission. It was warm, but not really hot. In fact, the transfer case was a lot hotter than the transmission.

My next step is going to be to remove the floor panel and pull the vent. I know, "check the vent first!" I did check it first, and the dust cap is loose. Now I'm going to pull it out and make sure it's not stopped up inside.

If that's not it, I guess it's time to pull the transmission and see what's going on around the input shaft. Bad gasket around the input shaft housing maybe? My understanding has been there isn't an input shaft seal to be bad, just some gaskets between some housing components.

I hate to pull the transmission. I only have one service bay big enough for these trucks, and the M817 is in it for some paint work on the bed.

Also, yesterday the tube feeding fuel to the manifold heater leaked onto the exhaust side of the turbo. That's never good. I had to change the ferrule to get it to stop. That could have been a right nice fire.

Oh well......back to work.

 

[stumps]

The vents have a bobble cap on the top, and inside of that cap is a light weight spring that presses a rubber disk onto a seat that is part of the vent fitting.

Moving the bobble cap only tells you that the bobble cap isn't crusted up with dirt. It tells you nothing about whether the vent is in working condition.

I find that after many months of sitting, the rubber washer, subject to continuous pressure from the spring, and a mild vacuum from the gear case, welds itself to the metal seat, effectively sealing the vent shut. When I removed the vents on my deuce, I took a 1/8 inch drill bit, and pressed its shank end into the hole in the vent, and tried to push on the rubber washer to lift it free. It took at least 5lbs of pressure on the drill bit to break the washer free of its bond. It should have taken only an ounce, or so.

I bought the fittings, and I am going to plumb all of my gear case vents into a common vent line that goes to the air cleaner. Enough of this stuff!

-Chuck

 

[Gamagoat1]

Around the input shaft there are bolts that hold the bell housing to the gearbox and the input shaft bearing cap in place. Each hole is a bore through to the inside of the gear box. If the bolts are installed without sealant they will eventually leak. My M35a2 leaked like mad, figured it was the rear engine seal. When taken apart the backside of the flywheel was dry but the clutch and pressure plate were soaked. The transmission was sitting on the bench and leaking at the bottom bolts. Removed each bolt added sealant and reinstalled. This is not mentioned in the TM 9-2520-246-34. Just says use a new gasket.
Also replaced rear seal just for practice. FIXED.

 

[rizzo]

Removed each bolt added sealant and reinstalled. This is not mentioned in the TM 9-2520-246-34. Just says use a new gasket.
Also replaced rear seal just for practice. FIXED.

what would be the best way to add sealant to the bolts? a thread sealant right? would locktite work?

 

[Gamagoat1]

I used TF-15 by jet lube of Canada on each bolt. 5 bolts hold the bell housing to the gear box and 4 bolts hold the bearing cap. I think loctite makes a great thread sealant that would work fine. Make sure the vent is clear.

 

[jwaller]

rtv will work just fine. make darn sure the bolt AND threads are free of ANY oil and let it dry before adding oil to it.

 

[m-35tom]

i think you will find that there are supposed to be copper washers on the bolts for the bearing retainer. anyway i have never done anything special to them otherwise and the last 20 did not leak. as for the vent, how can there ever be pressure in the trans when the input shaft is open to the clutch area so it can easily breathe there? just wondering.

tom

 

[Gamagoat1]

A copper washer is a good idea, however the TM and parts manual doesn't mention them, just lock washers. As far as the vent, good question, there isn't one........
BTW Tom ,you guys do some nice transmission work.!!

 

[Westex]

If you had the condition of a leak as described in this thread (mine was making oil and got past the main engine seal before I figured it out), would there be anything wrong with spraying out the clutch disk, etc at the local car wash as opposed to doing it with brake cleaner. Anyone tried this? I'm just thinking that hot soap, a good rinse and letting it dry out will clean it better than brake cleaner. I DON'T want to have to drop the tranny, 'cause it was operating fine before this leak.

 

[Westex]

bump

 

[jblack6527]

I would think that the car wash idea would possibly cause rust issues. Brake cleaner does a great job of removing oil, I would just stick with that.

 

[Westex]

Roger.

 

[mckeeranger]

I thought I would bring back an old thread instead of starting a new one.

Here is what I know:
I know I'm using the right gear oil.
I know it's not over filled. (Actually, it's almost 2 inches below the invert of the filler plug right now)
The transmission is not overly noisy and does not run hot.
The transmission shifts just fine.
The transmission vent is clear.

The problem:
The transmission leaks a few drops of gear oil per minute when warm and idling.
The transmission leaks enough for the clutch to slip under heavy loads or on steep grades when warm.
The transmission leaks about 3 oz. of gear oil when the truck is shut down warm.
All of this is from the bottom of the bell housing.

The plan:
I finished painting the bed on the M817 and moved it out of the shop. I plan to move in the M35 and pull the transmission when I get back from GA next week.

The question:
What am I looking for? Seriously, if the thing doesn't have a front seal, what could be wrong? I know it has a gasket on the input shaft housing and a plug over the counter-shaft bearing, but what if they are OK? Those are things that are highly unlikely to fail without something else going terribly wrong.

Don't get me wrong, this isn't my first rodeo. I've been turning wrenches longer than I care to admit. It's just the first time I've dug into a transmission that doesn't have a front seal. I'm afraid I'm going to pull it out and everything is going to look fine. Where would I go from there?

Thoughts anyone?

 

[agood1]

I took my truck out last weekend and ran some errands. Probably about 20 miles or so. All on local roads in traffic. I had no leak. But I am still concerned what it will do when I get it on the highway and run high speeds.
Just makes no sense, seems it should leak all the time. Not just when it feels like it.

 

[Gamagoat1]

mckeeranger ,
I know you'll get many opinions for this problem, but here is what I found and how it was fixed.
My M35A2 did exactly what yours is doing, leaking at the belhousing after a run. I figured it was a rear seal untill I removed the transmission. The clutch, transmission and inside of the bellhousing was soaked with transmission oil not engine oil. I pulled the flywheel and the seal was dry, with original install grease evident.
I put the transmission on the bench and left it till the next day. Next morning there was a little puddle of oil under the bell housing. Oil was coming from the bottom bolts that hold the bell housing to the transmission. First I checked to see if they were tight, they were. I looked at the drawings in TM9-2520-246-34 and noted that all the bolts (5) that held the clutch bell housing to the transmission were drilled through to the oil side of the transmission. The bolts that hold the input shaft bearing cap are also drilled clear through. At this point I removed the bell housing, replaced the gasket behind it, and replaced bell housing and bolts, using thread seal on all the bolts. I removed the input shaft bearing cap and replaced the gasket and bolts using thread seal on the bolts (4). Refilled the transmission according to the manual.

Now after about four hours of running time, and 30 miles at speed, it's still dry.
This sounds like a bunch of work for a little leak but it's not. If it's apart anyway it's a simple task to eliminate the possible problems. I n this case it worked. Make sure the bolts are tight,
60 to 80 lb-ft on the 5 bell housing bolts and 13-17 lb-ft on the 4 input shaft bearing cap bolts.

just my two cents!!!!!!!!!!!!

 

[agood1]

Thanks for the info.

In my case, I don't have a leak when the truck is sitting still, or even when it has been run for a moderate amount of time. Only after it has been run at highway speeds for an extended period (over 20 miles).

So, I would not expect the bolts to be leaking, otherwise they would be leaking all the time.

 

[m-35tom]

mike is right, leave nothing to chance. there are only a few things that can cause oil to get out the front. bolts, gaskets (2), worn bearing retainer, wrong front bearing. when all these are correct, propper oil level or even over full will not leak.

tom

 

[Gamagoat1]

When the transmission is hot the oil viscosity drops letting it leak through areas that it normally would not, or at a faster rate. The only way to really diagnose the problem is to take it apart. Every situation is different. It may be a rear main seal leaking and for the same reason, getting hot and thinning out. Or too light a weight oil in the transmission. If it's not a bad leak, leave it alone, if it effects your clutch then it should come apart.

 

[agood1]

Not engine oil.
Just changed the tranny oil with the proper oil as listed earlier in this thread.

My best option right now is "don't drive on the highway for extended periods".
So that is my plan. For now.

 

[Gamagoat1]

Does the oil leaking out smell like 90 W ???