TH400 frustration

[FluoFerret]

Sorry guys, I have to vent this now:

I just tried the 9th type of gasket on my TH400, and that damn thing still leaks between the pan and transmission-housing.

I even checked the joining surfaces with a straight-edge, checked the torque on the bolts many times and that damn thing still leaks.
I tried:
- rubber with steelcore
- cork
- neoprene
- silicone with aluminium core
- copper
- composite
- fiber

Now i will try one last thing: pull it all off, clean the surfaces (again) and put black liquid gasket on. can't be any worse than what i had now....

 

[78Malibu]

If you put it on with "the right stuff" it will not leak but its a little tough to get back off again too bad the gasket won't seal....

 

[Turbolq4]

Black "the right stuff" will work. You sure it's not leaking down from somewhere else and just looks like the pan?

 

[565bbchevy]

I always run aluminum trans pans and mine have a flat sealing surface so I have always used Holymar blue sealant with a quality gasket and have never had leak issues in my 400 transmissions

 

[Texas82GP]

Any chance it is leaking at the dipstick/fill tube? I had a leak there fool me once.

 

[1 RARE T]

You either have a pan that isn't as flat as it needs to be or excessive pressure blowing fluid out.

 

[Bonnewagon]

I never use gaskets dry. I don't care what type they are I always schmear some Ultra Black gasket sealer on every one. Not a lot, just enough to coat all surfaces. And be sure the surfaces are super clean- no oil. PS- when I was stationed in Germany in the 70's- Radio Luxembourg kept me sane.

 

[olds307 and 403]

What pan? I had a Hughes pan leak no matter what I did to it on multiple tansmissions.

 

[FluoFerret]

Any chance it is leaking at the dipstick/fill tube? I had a leak there fool me once.

i thought so too, but its dry there. it starts always somewhere around the pan.

You either have a pan that isn't as flat as it needs to be or excessive pressure blowing fluid out.

the pan is a cast aluminium deep pan made by B&M. i checked all the surfaces, they are all flat as they should be. excessive pressure would be a sign of overfilling, but the levels are just right, both hot and cold.

 

[Texas82GP]

i thought so too, but its dry there. it starts always somewhere around the pan.


the pan is a cast aluminium deep pan made by B&M. i checked all the surfaces, they are all flat as they should be. excessive pressure would be a sign of overfilling, but the levels are just right, both hot and cold.

Will the 4L80E gasket fit? I ask because I used the Delco gasket with the aluminum pan on my 4L80E. The Delco gasket was expensive but it seals with no sealer, at least it did for me.