leaking th400

richie 2 · 08-10-2020, 08:35 PM

with the pan off, dipstick in, the full mark is higher than the trans/pan surface. the modulator valve bore is right there too....sure seems to be seeping out there. the valve and o/ring fit feels sloppy. measured it all up and installed theres not much crush on the o/ring, .020" roughly...

Tom Goldman · 08-10-2020, 09:56 PM

Definitely run the fluid level at the add mark.
Another area I've had issues with lately is the shift shaft seal .
It appears the newer seals are not as tight on the shaft as ones I had from old kits.
My solution has been to machine a groove in the shift shaft and install an o ring .

Lenny5160 · 08-11-2020, 12:20 PM

Quote:

Originally Posted by Tom Goldman

Definitely run the fluid level at the add mark.
Another area I've had issues with lately is the shift shaft seal .
It appears the newer seals are not as tight on the shaft as ones I had from old kits.
My solution has been to machine a groove in the shift shaft and install an o ring .

That's interesting. I was just laying under my car last night after installing the engine and trans (glide) over the weekend, and noticed some fluid on the end of the shift shaft which I've not noticed before.

Bob Mulry · 08-11-2020, 02:15 PM

Just a quick heads up.....

Don't use RTV sealer on gaskets because it acts as a lubricant and allows the gasket to push out. Just completely clean both surfaces and use brake clean to remove any residual oil and use the gasket only...

OR

You can do like GM did, which was do not use a gasket at all. You can use anaerobic sealer or RTV, with the surfaces clean and bone dry put it together. Woks on engines and transmissions, just make sure it is allowed to dry and set up before exposing it to oil. This isn't for a race engine or transmission which is constantly being worked on, but it works great on a stock rebuild for the street.....

Your results may vary....

ss3011 · 08-11-2020, 03:18 PM

You really don't want to use any RTV sealants that will come in contact with ATF . Most ATF has an anti-foaming additive and RTV will destroy that additive . Most manufacturers that seal structures ( like case halves) will use a Poly-Acrylic sealer. PA has no effect on ATF.

Bob Mulry · 08-12-2020, 04:22 PM

Quote:

Originally Posted by ss3011

You really don't want to use any RTV sealants that will come in contact with ATF . Most ATF has an anti-foaming additive and RTV will destroy that additive . Most manufacturers that seal structures ( like case halves) will use a Poly-Acrylic sealer. PA has no effect on ATF.

Just a heads up.....

GM used that Orange RTV on TH700-4R transmissions and HT4100 engines for years....The surface has to dry and the RTV given time to completely set up.....

It's your choice...

Just sayin'

ss3011 · 08-12-2020, 08:54 PM

That RTV ended quickly after we in Engineering discovered the problems with the RTV's effect on the anti Foaming additives , and Off gassing that would rust internal transmission parts . Cadillac may not have had those problems with their engines , but most anything that was designed after GM's experience with "orange" RTV was either done with a gasket or the PA material I mentioned before .

08-10-2020, 08:35 PM	#1
richie 2 Senior Member Join Date: Feb 2009 Posts: 971 Likes: 428 Liked 205 Times in 93 Posts	Re: leaking th400 with the pan off, dipstick in, the full mark is higher than the trans/pan surface. the modulator valve bore is right there too....sure seems to be seeping out there. the valve and o/ring fit feels sloppy. measured it all up and installed theres not much crush on the o/ring, .020" roughly...

08-10-2020, 09:56 PM	#2
Tom Goldman VIP Member Join Date: Jan 2003 Location: Allentown,PA Posts: 2,477 Likes: 892 Liked 883 Times in 237 Posts	Re: leaking th400 Definitely run the fluid level at the add mark. Another area I've had issues with lately is the shift shaft seal . It appears the newer seals are not as tight on the shaft as ones I had from old kits. My solution has been to machine a groove in the shift shaft and install an o ring . __________________ Tom Goldman 1500 SG , 1506 STK

08-11-2020, 02:15 PM	#4
Bob Mulry VIP Member Join Date: Apr 2002 Location: Coarsegold, CA Posts: 1,016 Likes: 57 Liked 320 Times in 102 Posts	Re: leaking th400 Just a quick heads up..... Don't use RTV sealer on gaskets because it acts as a lubricant and allows the gasket to push out. Just completely clean both surfaces and use brake clean to remove any residual oil and use the gasket only... OR You can do like GM did, which was do not use a gasket at all. You can use anaerobic sealer or RTV, with the surfaces clean and bone dry put it together. Woks on engines and transmissions, just make sure it is allowed to dry and set up before exposing it to oil. This isn't for a race engine or transmission which is constantly being worked on, but it works great on a stock rebuild for the street..... Your results may vary.... __________________ Bob Mulry 7516 STK A & M Motorsports

08-11-2020, 03:18 PM	#5
ss3011 Senior Member Join Date: Feb 2002 Location: Southeast Michigan Posts: 909 Likes: 70 Liked 239 Times in 114 Posts	Re: leaking th400 You really don't want to use any RTV sealants that will come in contact with ATF . Most ATF has an anti-foaming additive and RTV will destroy that additive . Most manufacturers that seal structures ( like case halves) will use a Poly-Acrylic sealer. PA has no effect on ATF.

08-12-2020, 08:54 PM	#7
ss3011 Senior Member Join Date: Feb 2002 Location: Southeast Michigan Posts: 909 Likes: 70 Liked 239 Times in 114 Posts	Re: leaking th400 That RTV ended quickly after we in Engineering discovered the problems with the RTV's effect on the anti Foaming additives , and Off gassing that would rust internal transmission parts . Cadillac may not have had those problems with their engines , but most anything that was designed after GM's experience with "orange" RTV was either done with a gasket or the PA material I mentioned before .