what is the trick to keep a transmission pan from leaking? I bought a brand new tci th400, and it leaked.. Took the pan off brushed the surfaces... Put new gasket on, with some gasket maker.. Still leaks. Got a transmission rebuilt in my old truck,, got it back.. Leaked. Every transmission ive had has leaked.. I take the pan off,, try to straighten the holes.. put new gaskets on. Make gaskets.. They all leak. What am i doing wrong? thanks

 

Make sure the pan and case surfaces are as clean and dry as possible. Use paper gaskets, stay away from cork. No gasket maker and torque by hand, about 10ftlbs. should do.

 

so no permatex? the gasket i had was rubber i believe... THe gasket i took off was rubber too. every chevy transmission ive had has leaked,, I figured a brand new tci would be good, but it leaked out too. maybe i'm tightening it too much? didnt really seem like it...

 

are you sure its not the plug leaking?

 

Over tightening will distort the pan and it will only make contact where the screws are. Especially if using cork gaskets or rubber gaskets without O rings around the screw holes. The O rings are there to prevent over tightening, and should not be squished flat.

 

its not the plug. There's no O rings on the bolts. I tried flattening out the bolt holes some, they were pulled out a little, but its hard to do with that lip thats there. Im pretty sure it was a rubber gasket, just went to Advance and asked for a gasket for a th400.

 

More than likely you are OVER tightening and distorting gasket. There small bolts,torque to spec and use loc tite, I never get leaks that way

 

If you're having problems with using gaskets, then use this and no gasket at all: http://www.permatex.com/products/aut...sket_maker.htm
I've used it on oil pans, trans pans, rearend covers, etc. Button the bolts down snug, but don't horse em on super tight. After the silicone sets up, tighten the bolts just a little more for good measure.

 

i used that stuff along with the rubber gasket.. Not a whole bunch, but just a little. still leakin.

 

Which is exactly why I suggested NOT using a gasket with the silicone, since you're having leaking problems with them. It's simple math...transmission body+both sides of gasket+pan=4 gasket mating surfaces, and 2 possible gaps to leak. No gasket, but silicone gasket maker instead=2 gasket mating surfaces and only 1 gap. It's called lessening the odds.