Transmission Leak....

for what it is worth, too light weight oil will not leak, if there are no problems. i use 30 wt motor oil and
on one test transmission i over filled by 2 qts (total of 7 qts) no leads at 62 mph for hours.

m-35tom said:

for what it is worth, too light weight oil will not leak, if there are no problems. i use 30 wt motor oil and
on one test transmission i over filled by 2 qts (total of 7 qts) no leads at 62 mph for hours.

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Key words here are "If there are no problems" If the bolts were not tightened right or have loosened up a little they sure will leak.

I'm real surprised that with that much oil it doesn't migrate out the inputshaft bearing cap, it's open, no seal...

well, that is the point! there has to be something wrong, not over full or thin. those two just won't do it, even togeather.
(even 7 qts is well below the top shaft.)

My leak is definitely the transmission not engine oil.

Went ahead and dropped transmission

OK, so I didn't wait until next week, I went ahead and dropped the transmission this evening. ( I get impatient sometimes )

I didn't find a "smoking gun" but found something suspicious near the bottom of the bell housing gasket.

The counter shaft plug was filled with grease that dumped out when I pulled the bell housing off. I don't know that it matters, since the gasket should seal that area completely. The gasket around it appears saturated with grease in an area that should be isolated from it.

The bell housing and input shaft housing bolts all had thread sealer on them, but the one at the bottom of the bell housing did not have as much as the others.

The input shaft gasket appears to have been well sealed. There is no sign of saturation, and the bolts all had plenty of thread seal on them. The input shaft was surprisingly dry, so I don't think anything was coming out there.

At this point, I'm going to call it a failed bell housing gasket and thread seal around the bell housing bolt.

What do you guys with more experience think?

The pressure plate, throw out bearing and pilot bushing all look good. Since there was no "chatter" in the clutch, I'm just going to replace the disk and be done with it. The truck has about 7600 miles on a depot rebuild.

It's a shame about the disk though, it had a lot of meat left on it.

Just from your picture I'd say it was the counter shaft plug leaking. The gasket at the bottom under the plug looks pretty soaked. If you are this far why not pull the flywheel and check/replace the rear seal? Your well on the road to doing a great job.

mckee, did you leave the PTO on that tranny when you dropped it?

Gamagoat1 said:

Just from your picture I'd say it was the counter shaft plug leaking. The gasket at the bottom under the plug looks pretty soaked. If you are this far why not pull the flywheel and check/replace the rear seal? Your well on the road to doing a great job.

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I'm 99.9% sure the plug leaked, as the cavity between it and the bell housing was filled with grease. Should it seal as tight as a freeze plug, or should the bell housing gasket contain it? If it should seal, then it is probably the culprit.

I will be pulling the flywheel and changing the rear main seal. There is no sense in not doing it this far in.

Normally I would replace the entire clutch assembly, but with only 7,000 miles on it since a rebuild, I think parts that don't deteriorate with age should be OK.

Seals, gaskets, and the clutch disk, on the other hand, will all be replaced. Assuming they were from the depot overhaul in 1990, they are 20 years old. With no rust present, I think the pressure plate, throw out bearing, and pilot bushing should be OK.

clinto said:

mckee, did you leave the PTO on that tranny when you dropped it?

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Yes, I did. I figured dropping the transmission with it on wouldn't be a problem, and it wasn't.

However; Leaving it in place while lifting everything back in may not be an option. It's off-center weight, and the tight squeeze between the frame, brake components, and the front drive shaft may be too much of a hassle. (Yes, I was to lazy to remove the drive shaft)

I did make some alignment pins by cutting the heads from a couple of long bolts, but I'm afraid the PTO may keep the transmission in too much of a twist. I don't have an adjustable spreader, just a chain.

absolutely no reason to replace the disk if it is the propper thickness. just clean it in some degreaser and it will be as good as new.

m-35tom said:

absolutely no reason to replace the disk if it is the proper thickness. just clean it in some degreaser and it will be as good as new.

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That's good news. I'm not concerned with the cost as much as the couple of days it would take to get one delivered.

I've already replaced the rear main, and cut new gaskets for the input shaft housing and bell housing. If I don't have to order a counter shaft plug, it's ready to go back together now.

That brings me back to the question: Does the counter shaft plug have to seal like a freeze plug, or does the bell housing gasket trap the grease in the cavity between the housing and the plug?

Any other transmission I've worked on with plugs on the outside like this, they have to seal tight. I don't know about this one, because it's the only one I've ever seen with the transmission to bell housing gasket configured like it is.

Life was so much simpler when I only worked on flathead fords.

Gamagoat1 said:

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.

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Old thread - but WHAT @Gamagoat1 SAID!!!!