TH350 still leaking
Thread Starter
Burning Brakes
Joined: Sep 2017
Posts: 1,073
Likes: 65
From: Belgium
TH350 still leaking
Hi everyone
My 77 TH350 is still leaking.
It seems the fluid drips come from above (I'm not 100% sure.)
I want to replace all the O-ring seals, dipstick seal and use a Moroso thick rubber gasket (93102), and be done with it.
Do you guys know the O-ring seals and dipstick seal part numbers? (I'm from Belgium so I buy on Ebay or Amazon)
Are there other places on the th350 where leaking is common?
My 77 TH350 is still leaking.
It seems the fluid drips come from above (I'm not 100% sure.)
I want to replace all the O-ring seals, dipstick seal and use a Moroso thick rubber gasket (93102), and be done with it.
Do you guys know the O-ring seals and dipstick seal part numbers? (I'm from Belgium so I buy on Ebay or Amazon)
Are there other places on the th350 where leaking is common?
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
You may have to get longer pan bolts with that blue silicon gasket.
Modulator has an "O" I believe between itself and the trans body.
Modulators rubber lines crack from exhaust heat and / or the hose clamps are shot.
The shift linkage shaft can drip. Supposedly there is a seal that can be slipped in there after the linkage is moved. Try YouTube for that procedure.
Tail-shaft housing seal. Requires driveshaft removal and tail shaft housing removal. Support tranny with jack, remove trans mount, then four bolts with long 3/8" extension and housing comes out. And speed-o comes off. "O" ring seals on that too.
The dipstick "O" ring is std size at parts store but must be ATF compatible.
Modulator has an "O" I believe between itself and the trans body.
Modulators rubber lines crack from exhaust heat and / or the hose clamps are shot.
The shift linkage shaft can drip. Supposedly there is a seal that can be slipped in there after the linkage is moved. Try YouTube for that procedure.
Tail-shaft housing seal. Requires driveshaft removal and tail shaft housing removal. Support tranny with jack, remove trans mount, then four bolts with long 3/8" extension and housing comes out. And speed-o comes off. "O" ring seals on that too.
The dipstick "O" ring is std size at parts store but must be ATF compatible.
2026 Loser of the Year
Joined: Sep 2013
Posts: 36,595
Likes: 7,042
From: New Or-leens Loo-z-anna
Also...there is a small (1/4" diameter ?) metal tube vent on top of the transmission case.
Sometimes the transmission will "burp" fluid out of the vent tube.
The fluid will trickle down the trans case causing it to appear that the trans is leaking in other locations.
Also...in the tube vent is clogged, trans. pressure will force fluid out of all the seals, gaskets, and orings.
First try working an old wire clothes hanger into the tuce vent to make sure it is not clogged before replacing seals, etc.
Sometimes the transmission will "burp" fluid out of the vent tube.
The fluid will trickle down the trans case causing it to appear that the trans is leaking in other locations.
Also...in the tube vent is clogged, trans. pressure will force fluid out of all the seals, gaskets, and orings.
First try working an old wire clothes hanger into the tuce vent to make sure it is not clogged before replacing seals, etc.
Racer
Joined: Nov 2019
Posts: 336
Likes: 173
From: Canadian living in southern France
It may not look like it's coming from the top, but I replaced the O-ring on the speedometer cable fitting, and that cured most of my problem. It's not difficult, and if your's is the original, it is probably old and cracked like mine was.
Also, look at Corvette specialists and Rock Auto for parts. I've had excellent service from both.
If you need any help or advice, send me a message. I pretty much restored my C3, mechanically, (the body and interior were good), here in France.
Also, look at Corvette specialists and Rock Auto for parts. I've had excellent service from both.
If you need any help or advice, send me a message. I pretty much restored my C3, mechanically, (the body and interior were good), here in France.
Last edited by hdeyong; Jul 7, 2022 at 09:15 AM. Reason: addition
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
It may not look like it's coming from the top, but I replaced the O-ring on the speedometer cable fitting, and that cured most of my problem. It's not difficult, and if your's is the original, it is probably old and cracked like mine was.
Also, look at Corvette specialists and Rock Auto for parts. I've had excellent service from both.
If you need any help or advice, send me a message. I pretty much restored my C3, mechanically, (the body and interior were good), here in France.
Also, look at Corvette specialists and Rock Auto for parts. I've had excellent service from both.
If you need any help or advice, send me a message. I pretty much restored my C3, mechanically, (the body and interior were good), here in France.
