Leaking th350

[Magic1]

Does anybody have any tricks on getting the transmission pan on a th350 to be leak free?  I've replaced the pan itself and have tried permatex to no avail. I've seen a rubber gasket with a metal core that supposedly won't blow out or getsucked in but I ddon't wanna keep throwing money at it and dropping the pan is getting old. Lol

[Captkaos]

Are you putting the gasket and permatex on and not letting it skin or cure per the instructions?

[Magic1]

I put a thin layer of permatex on the pan followed by the gasket and another layer of permatex between the gasket and transmission. Finger tightened all the bolts and let it sit for about an hour. Then snugged up all the bolts and filled with fluid. It stayed nice and dry for about two weeks and now leaking again. 

[ehjorten]

Are you sure it is the pan leaking and not the pump seal or something else?  Is it leaking while driving or does it only leak when it sits for a couple of weeks?

If it is the pan...have you put a straight-edge to the mating flanges to make sure it is flat?

[Magic1]

It leaks whether sitting or being driven.  I'm assuming it's the pan since it seemed to stop completely for a couple of weeks after using the permatex on the gasket and pan. I didn't use a straight edge on the pan because I didn't see a need with the pan being brand new. When I drop it again I'll check it.

[ehjorten]

Dipstick o-ring?

[VileZambonie]

OK there is no need for an RTV sandwich. Either use a gasket or use RTV not both. Are you certain it is leaking from the pan? there's lots of other areas prone to leakage including the detent cable, shift shaft seal, dipstick tube seal, front pump, torque converter seal, tail shaft seal etc. If you clean it off real good and park it in a dry spot just look for the highest point that has fluid on it. You can go one step further and use dye tracer with a UV light to pinpoint it as well.

[Magic1]

I'm almost positive that it' the pan but I'm not sure. It seems to leak around the corners. I'll have to do a little more looking

[Captkaos]

If you use permatex I would only use it on the cover side and a skim coat (THIN) to get the gasket to stick.  Let it dry and lift it up.
If you put some on both sides it is probably squeezing out the gasket.  Like Vile said you don't want to make a silicone sandwich.