Leak from the Bellhousing

Ok, read loads of threads but nothing seems to peg this.

Started w/ a bad tranny, swapped that one out. Ever since we put in this one I've had a leak from the bellhousing. Did the the "drop the gear oil level down to 2 knuckles" that stopped it from pissing out while we drove, it would still dump a handful when we shut it off.
It did make the clutch slip in 4 & 5 gear ( I know that is torque related ?) Pulled the access cover and did a good clean w/ brake cleaner. That stopped the slip.
The gear oil is now almost out of reach (cold) and it still leaks. Drips about once every 5 secs at an idle, after running at speed. When I shut it down it still dumps a handful.
Is there somewhere other than around the shaft that it could be leaking from? I've checked the engine oil and don't seem to be losing it from there. I've smelled it and it smells like gear oil, . . . I think.

Hoping to get this sorted out soon as we are planning a month long trip in this rig and I'd hate to be spending most of my time under it

LowTech

The shaft doesn't really have a seal. It is surrounded by a fairly long sleeve that is a close fit to the shaft. The first gear on the input shaft tends to fling the oil away from the bearing and shaft.

However....

There is a cap that is bolted on the front of the transmission that holds the input shaft sleeve, and it has four bolts and a gasket holding it in place. If the gasket is compromised, or the bolts don't have sealant on them, they will drip, drip, drip forever. If the bottom bolt is missing, it will spew.

-Chuck

In one of the other posts, someone (I think M35Tom) mentioned there is 2 different input shaft bearings. One is open and one is shielded. Might want to try to find that thread. Personally, I would drop the level a bit more. I can only reach my GO if my fingernails have not been cut in a week! Are you using regular or synthetic?

stumps said:

There is a cap that is bolted on the front of the transmission that holds the input shaft sleeve, and it has four bolts and a gasket holding it in place.

-Chuck

Click to expand...

Stumps, Thank you very much.
I'm guessing the "cap" is on the outside, behind the throwout bearing? One of those things that require the tranny to be dropped I was thinking that I was headed that way.

LowTech

gimpyrobb said:

In one of the other posts, someone (I think M35Tom) mentioned there is 2 different input shaft bearings. One is open and one is shielded. Might want to try to find that thread. Personally, I would drop the level a bit more. I can only reach my GO if my fingernails have not been cut in a week! Are you using regular or synthetic?

Click to expand...

Gimpy, that was one of the first threads I read about this issue. In fact I've passed that info on to the man that has been my M35 teacher . . . made me feel smart!
I'll check the level again in tomorrow and see how far down it's gone. It just makes me nervous when the GO gets low . . . you know, second tranny and all.

Thanks for the reply,
LowTech

LowTech said:

Stumps, Thank you very much.
I'm guessing the "cap" is on the outside, behind the throwout bearing? One of those things that require the tranny to be dropped I was thinking that I was headed that way.

LowTech

Click to expand...

Yes, you do have to back the transmission away from the engine to get to it. There really isn't much else that could account for the leak.

Here is a snapshot from TM 9-2320-361-34P.

-Chuck

Bump

Did this ever get solved? I have the same problem.

Thanks
Jim

Have you checked your vent? Sounds sort of simplistic, but if the vent is plugged the only place the heat can go is out the pores and narrow spots such as the input shaft.
These are often over looked on axles and become the sources of leaking seals, but the transmission has one too as well as the transfer case. It might be a good idea to double check that the vent is in fact open.

Hope this is helpful
RL

gimpyrobb said:

In one of the other posts, someone (I think M35Tom) mentioned there is 2 different input shaft bearings. One is open and one is shielded.....

Click to expand...

The correct one is the #308ZNR. Z stands for shielded on one side only, that is facing the inner side, opposite to the groove & snap-ring (might want to check this very old thread here: https://www.steelsoldiers.com/showthread.php?4026-m35-tranny-input-shaft.html

I think the shield is there mainly to prevent too much oil from getting past the bearing into the bearing retainer cavities. There is a small oil return hole provided at the bottom of that cover. If this gets "overflowed" there is no seal but just that threaded portion inside the bearing cover to keep oil from leaking past the input shaft. Needless to say that both, the return hole and this internal thread must be kept free of gunk/old grease/sealant/etc. to function properly.

BTW: I have never had a correctly assembled transmission leaking from the input, and I always keep the oil level up to the fill plug....

G.

rlwm211 said:

Have you checked your vent? Sounds sort of simplistic, but if the vent is plugged the only place the heat can go is out the pores and narrow spots such as the input shaft.
These are often over looked on axles and become the sources of leaking seals, but the transmission has one too as well as the transfer case. It might be a good idea to double check that the vent is in fact open.

Hope this is helpful
RL

Click to expand...

Have checked them, not only checked them I took them out and pushed them open from the inside w/ the back-side of a drill bit. Just to make sure that they weren't stuck.
We haven't put to many miles on it since I started this thread, w/ the build going on.
It does seem to have almost stopped now that it's down to the "two knuckle" fill level. I've used it a few times and had no drip, then I used it at hyway speed one day and it puked up some. I think it just got hotter and that raised the level enuff to leak.

I will be keeping close watch on it while we are on this trip . . . if we can ever get out of here

Thats what happened to me! It was fine till I hit the highway, then it puked all over. I ended up draining enough to fill the 20 oz Mt.Dew bottle I had with me. It has been fine ever since.

Also the bolts that hold the bellhousing to the trans can leak if they are loose.Also if the guide pins are missing it can cause it to leak past the input shaft as it will force the input shaft to one side or the other..this can also make the trans hard to shift and possibly be noisy to. That was the case with my truck .the bell to trans bolts had worked loose one was all the way out the others were holding on by like one or two threads.Trans was leaking and really hard to shift.You would have thought the syncros were shot cuz it was grinding so bad

tiger422 said:

Bump

Did this ever get solved? I have the same problem.

Thanks
Jim

Click to expand...

gringeltaube said:

. . . There is a small oil return hole provided at the bottom of that cover. If this gets "overflowed" there is no seal but just that reverse-threaded portion inside the bearing cover to keep oil from leaking past the input shaft. Needless to say that both, the return hole and this internal thread must be kept free of gunk/old grease/sealant/etc. to function properly.

BTW: I have never had a correctly assembled transmission leaking from the input, and I always keep the oil level up to the fill plug....

G.

Click to expand...

And the winner is . . .

Spent yesterday under the rig pulling the tranny out, it had gotten too low and was still leaking after being driven at hyway speeds. Pulled off the cover plate and found, 1) that the cover plate bolts were not tight (enough, by my standards, but not the leak) and that 2) some high quality mech wrench had used . . . oh . . . maybe half a tube of sealant, around the cover plate edge and had successfully filled the return drain hole. Never putting a tranny in again w/o pulling that plate off.

Cleaned everything, picked out the return hole & and the spiral grooves, made a new cover plate gasket, (brushed it lightly w/ sealant) and put it all back together w/ a bit of lock-tight on the bolt threads.



I will def keep an eye on it once we start driving.

Something that I did notice, if the leak is causing the clutch to slip it has to be coming from around the input shaft. any other leak would just run down the front of the tranny and drip out w/o getting into the clutch area.

Hope this helps, and all subscribers can now send in their $10 to my personal account

Glad you solved that problem....!

Now, as for clutch slippage, it can (and does) also happen if enough engine oil is leaking past the rear main seal into the bellhousing.
The problem as I see it is that at 50mph, instead of flowing directly down and out at the bottom drain plug the oil gets picked up and swirled all around inside the housing, by a 100+ knot (120mph!) wind stream or better say hurricane, from the flywheel spinning close by @ 2500RPM! The pressure plate then will act like an impeller, continuosly sucking air + oil mist in in the center area and slowly wetting all clutch components and surfaces involved.

G.

gringeltaube said:

Glad you solved that problem....!

Now, as for clutch slippage, it can (and does) also happen if enough engine oil is leaking past the rear main seal into the bellhousing.
The problem as I see it is that at 50mph, instead of flowing directly down and out at the bottom drain plug the oil gets picked up and swirled all around inside the housing, by a 100+ knot (120mph!) wind stream or better say hurricane, from the flywheel spinning close by @ 2500RPM! The pressure plate then will act like an impeller, continuosly sucking air + oil mist in in the center area and slowly wetting all clutch components and surfaces involved.

G.

Click to expand...

I agree that leakage from the tranny is NOT the only reason that there can be clutch slippage. Engine oil leakage was not our prob, we've not lost a bit of engine oil since we did our first oil change. What I meant was that if one is leaking GEAR OIL from the tranny, out the bell housing AND the clutch is slipping, I would think that it had to leak out from the input. I do see your point about the pressure plate sucking air into the center.

Well . . . it seemed like a good thought when it popped into my head

Thank you for all input on this subject, Stumps / Gimpy, it sure made me feel a bit more confident as to what I was looking for and how to fix it

I agree that oil leaking past the rear seal can cause the clutch to slip. I heard the same story from a Seabee next door. According to him driving a deuce above 50 mph will cause this problem. His solution was to spray brake cleaner on to the pressure plate to clean the oil residue off.