Technical GM TH350 Tail Shaft Leak FIX?

I recently posted about my ongoing issue with my TH350 leak, and for some reason my post disappeared, so trying again. I had the classic issue where tail shaft leaked through weep hole in the output yoke. I solved it by replacing the yoke with a sealed yoke (no weep hole). At this point I have a leak from the rear tailshaft housing seal. I have replaced it twice, and have replaced the tailshaft sleeve 1 time, but I still have the leak. My question is, has anyone used ACDELCO part # 8654063 pictured below to solve a TH350 rear tailshaft housing seal leak?

 

Don't know anything about that seal, but just wondering if you checked the vent tube on the case. If the trans builds up pressure, even a new seal can leak. Just a thought.

 

that sleeve & O ring is for sealing the yoke with the weep hole. Is the oil getting past the seal lip ?, or between the seal and the aluminum tail housing.

 

I'm gonna check the vent tube tomorrow. The fluid is getting past the seal lip so maybe I'll find an issue with the vent. Potshot, if I get to a last resort situation does it make sense if I use the 8654063 sleeve and o-ring?

 

I had one that was leaking at the dipstick tube entry point. I wound up using some green AC O rings to seal it. Had to make up a bracket to hold it tight close to the transmission.

Yours might be leaking from there and running down to the tail shaft like mine was.

Might try that...

 

How's the bushing in the tail housing? If it's okay, you might want to check the drive shaft for balance and run-out.

 

Does it leak overnight or over a period of days?

 

If normal methods like seal replacement do not work, look for bad U joint, bent or out of balance drive shaft.

 

I haven't figured out why, but I have proven that large amounts of fluid (about 2 quarts) is making its way into the tail housing, so the reason it is leaking from the tail shaft seal is that the seal simply isn't designed to hold back that amount of displaced fluid. Has anyone seen a failure like this?

 

..And how did you prove this?

 

Mark,
I removed the tail housing 3 times, after running and driving the truck, an each time the housing was filled with approximately 2 quarts of fluid. Is that not proof?

 

No, it's not .The tailhousing receives and drains ATF through a hole into the main oil pan area. A bit more would come through the rear case bushing and governor lube, but that's about it. I doubt that a short tail would even hold 2 qts, full to the top. If it does, your entire case would be full , right about up to the vent tube!

 

Is this turbo 350 out of a buick ?What year

 

27 quarts of ATF is just too much! But seriously, how many quarts did you use? Sometimes, we don't pay too much attention to what we're doing, sort of like me hitting a key that changed the font/lettering of my response (???). The book says PINTS, and we substitute QUARTS. I'd say drain it ALL out, including the torque converter if it has a drain plug, and start over. Nothing wrong with recycling the ATF, as long as you keep it clean and filtered. Now, can you help me out with this change in the font/lettering? I'm just NOT a computer guy! (I just had surgery on my left hand for release of TWO trigger fingers, and it's messing up my typing!) I am Butch/56sedandelivery.

 

Ok, maybe I exaggerate just a wee bit , I drained it into a gallon jug and wasn't sure about the exact amount, but was sure that it was too much. I just went out and transferred it to a 1 quart bottle and it filed it up. Can we agree that even 1 quart is too much and would be more than the tail housing seal can stop? If that is the case, what could cause that much fluid making it's way to the tail housing?

sdluck,
Why do you ask if it's out of a buick, is their something about a turbo 350 out of a buick that I should know? I'm not sure what it originally came out of. The guy I bought it from had it rebuilt and used it in an early 50's Ford for a very short time and ended up removing the SBC/TH350 and went to a SBF/AOD combo. He didn't know what it started its life in.

Butch,
Last thing I did was drain the tail housing, drain the pan, and add 4 quarts to rule out the possibility that I had somehow overfilled it. I will drive it a couple days, checking the fluid level frequently, and watch for leakage. I think the 6th item from the left at the top of your reply box "font family" should help with your issue . I had a trigger finger surgery on both hands a while back, so I feel for ya.

 

Two trigger fingers on one hand????? Do you have 6 fingers on your left hand? How do you know which finger to hold up when someone pisses you off?

 

Thumb on one hand and pinky on the other hand, and the pissed off finger has a mind of its own

 

Okay. Just jack it up from the rear and let it sit overnight. Just loosen the tail bolts and pull it back a tad. Shouldn't drain much at all. I doubt that's your problem.
Any drive line vibrations..Low or high speed ?

 

Mark,
I didn't mention earlier, but, I had Cincinnati Driveline replace the weep hole type output yoke with a new yoke without a weep hole because the leak was originally coming out of the tail housing around the seal AND thru the yoke. They balance the drive shaft, so no drive line vibration at any speed. I'll definitely do what you're suggesting, but I'm thinking it will leak allot. What is your theory with the test?

 

Thanks ALL for the interesting conversation this fine night, but this ugly old man needs his beauty rest so I'll check back in sometime tomorrow. Something else I should mention is that this issue isn't with my 54 Ford, but, rather with my 76 Chevy C20 pickup.

 

Okay, that's probably a long tail, but it still should drain back down fairly low.
Let us know.

 

Butch, it looks like you just hit the bold symbol. Just hit it again and you should be back to normal.

 

Trigger finger sucks. I've got one that I need to get fixed. When it locks up it hurts like crazy, and I need to pull it back straight with my other hand.

 

If the unit is overfilled, it will overflow out the vent. If the vent is plugged, it will usually blow out of the fill tube.
As a previous poster suggested, make sure the bushing is good. The only way it can get past the seal lip, is a loose bushing, bad seal, or the finish on the yoke. ( a groove or too rough a surface)

 

There must be a return passage so fluid can return from the tail shaft to the body/pan.Have you checked to see if its there,and still open?

 

I do not if a TH 350 has this but certain early transmission torque converters drained down after sitting. This caused the lower pan to fill and also fill the tail shaft housing thru it's drain hole. After starting it refills very quickly so no harm no foul but depending how much would cause some to go by the bushing to the seal. Good luck

 

Converter drainback is pretty common on the 350, especially when they get some miles on them, and the pump bushing gets worn.

 

Inspect the extension housing lip seal and make sure that it's garter spring is in place. It provides tension to hold the seal snugly against the seal surface.


https://en.wikipedia.org/wiki/Garter_spring

 

If half the converter drains down overnight and the truck is sitting level, I don't believe the fluid height would be up to slightly below the centerline of the trans output shaft. Still, as you say, it would go down to dipstick full level in a hurry.
Still no reason for the rear seal to leak, even if was completely covered.

 

Are you sure it's leaking from the speedometer drive connection?