THM350 Shift Shaft Seal Replacement
Thread Starter
Racer
Joined: Apr 2006
Posts: 340
Likes: 0
From: Warrensburg MO
THM350 Shift Shaft Seal Replacement
Anyone with experience on this topic. My shift shaft seal is leaking, and I plan on replacing it. I think there is a special tool for this, but am wondering if anyone knows of an alternative method without the special tool. Thanks..
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From: Corsicana, Tx
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No special tool really needed. There is the right way...and the easy way.
The right way is to drop the pan, unbolt the linkage inside and outside. slide shaft out and then use a screwdriver and pry out old seal. Then you can install the new one with a small socket to drive it in. Then reassemble everything.
The easier way that MIGHT work, is to remove linkage on outside of trans only and dig out the old seal with a small icepick or something. Then drive a new seal in.
You can also usually just drive the old seal in deeper and install another seal on the outside of it. The bore is usually deep enough.
With either method, a bullet proof way is to install two seals in there regardless.
Make sure shaft isn't scored up any. If it is,. make sure the new seal rides in a new place on it.
JIM
The right way is to drop the pan, unbolt the linkage inside and outside. slide shaft out and then use a screwdriver and pry out old seal. Then you can install the new one with a small socket to drive it in. Then reassemble everything.
The easier way that MIGHT work, is to remove linkage on outside of trans only and dig out the old seal with a small icepick or something. Then drive a new seal in.
You can also usually just drive the old seal in deeper and install another seal on the outside of it. The bore is usually deep enough.
With either method, a bullet proof way is to install two seals in there regardless.
Make sure shaft isn't scored up any. If it is,. make sure the new seal rides in a new place on it.
JIM
Race Director
Joined: Jul 2004
Posts: 12,706
Likes: 329
From: Scottsdale Arizona
Originally Posted by 427Hotrod
No special tool really needed. There is the right way...and the easy way.
The right way is to drop the pan, unbolt the linkage inside and outside. slide shaft out and then use a screwdriver and pry out old seal. Then you can install the new one with a small socket to drive it in. Then reassemble everything.
The easier way that MIGHT work, is to remove linkage on outside of trans only and dig out the old seal with a small icepick or something. Then drive a new seal in.
You can also usually just drive the old seal in deeper and install another seal on the outside of it. The bore is usually deep enough.
With either method, a bullet proof way is to install two seals in there regardless.
Make sure shaft isn't scored up any. If it is,. make sure the new seal rides in a new place on it.
JIM
The right way is to drop the pan, unbolt the linkage inside and outside. slide shaft out and then use a screwdriver and pry out old seal. Then you can install the new one with a small socket to drive it in. Then reassemble everything.
The easier way that MIGHT work, is to remove linkage on outside of trans only and dig out the old seal with a small icepick or something. Then drive a new seal in.
You can also usually just drive the old seal in deeper and install another seal on the outside of it. The bore is usually deep enough.
With either method, a bullet proof way is to install two seals in there regardless.
Make sure shaft isn't scored up any. If it is,. make sure the new seal rides in a new place on it.
JIM
I did it "the right way." No special tools needed and no leaks either. What you have to be VERY careful about is making sure that you put all the linkages together properly. Otherwise, you won't be able to shift into any gear and have to take it appart again.
Ask me how I know.
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Joined: Jul 2004
Posts: 12,706
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From: Scottsdale Arizona
Originally Posted by knbwag73
Where can I get a replavement seal?
Thanks
Race Director
Joined: Jan 2000
Posts: 13,018
Likes: 2,262
From: Corsicana, Tx
2020 C2 of the Year - Modified Winner
2020 Corvette of the Year (performance mods)
C2 of Year Winner (performance mods) 2019
2017 C2 of Year Finalist
T-400 is the same way. It's not that hard to drop the pan and do it the "official" way...probably need to change filter and install a shift kit anyway right?
Either way, two seals is a good idea.
JIM
Either way, two seals is a good idea.
JIM
Thread Starter
Racer
Joined: Apr 2006
Posts: 340
Likes: 0
From: Warrensburg MO
Originally Posted by kevinator80
After digging at one of these for atleast an hour and risk scoring the sealing surfaces, I think I would try 427Hotrod's idea the next time I have to do one.
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Race Director
Joined: Jul 2004
Posts: 12,706
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From: Scottsdale Arizona
Originally Posted by tommyleea
A friend of mine had the special tool to change the seal. Works like a charm. 5 minute job. Remove linkage, slide tool over the shaft. The tool screws in and grabs the seal. Then you turn a bolt that goes in the center of the tool. It presses on the shift shaft and pulls the seal out. Then tap in a new seal. No more leak. Tool can be had at MATCO or Snap-ON for 25.00. I have one now. Cheers.
Le Mans Master
Joined: Jan 2003
Posts: 6,575
Likes: 1
From: Tuttle OK
Cruise-In VIII Veteran
It is my personal experience that the very best way to handle a THM350 shift shaft seal replacement is to yank the transmission and replace the entire unit with a 700 R4..
