Transmission leak

[Chevyman680063]

Does anyone have any idea why my transmission keeps leaking from the pan gasket? It did not leak for a while after I got the truck but it started leaking about 1 1/2 to 2 years ago. I have already had 2 pan gaskets put on it and both of them have ended up leaking. The first one that was put on went a few months before it started leaking again then the second one that was put on started leaking about a week or 2 later pretty badly. The bolts appear to be tight enough, but I'm wondering if they're too tight or worse, the pan or transmission surface is warped. The transmission is a TH350 automatic.

[Green Machine]

First, don't use the rubber/cork gaskets, too easy to overtighten, get the stiff black from NAPA or somewhere. Pan must be flat, put pan edge on a flat solid suface and tap all the pan bolt holes down, and check the corners too. Do not use any sealer with any gasket, makes it ***** to remove and just lubricates the gasket making it squish out all over.

But you really have to make sure the pan is what is really leaking, could be cming from the converter hub seal, pump o-ring or pump bolts on the front or from several places on the side.

[truckdude239]

try changing the pan sounds like the pan is wraped

[Geezer]

Over tightening the bolts usually causes the gaskets to split and leak. I prefer the black rubber gaskets but I can use the cork ones if I’m careful. As far as sealer goes, I always use Permatex #1 or 2 on the pan side because if can be cleaned off with a wire wheel off the vehicle, but I don’t put anything on the tranny side of the gasket except maybe antisieze, but I don’t usually even do that. Leaks at the shaft where the shifter goes in and leaks at the speedo gear shaft may look like the pan is leaking….

[krue]

Replace all the seals on it. Front and rear, shift shaft, kickdown cable o-ring, dipstick o-ring and speedo gear o-ring.

[Don Smith]

I had a similar problem, turned out to be the dipstick tube o-ring.

[DangerBoy]

I'm fightin the same battle right now with the same exact things goin on. The seals are my next project.

[ChevyCrazy67]

If it does turn out to be the pan causing it to leak like green machine said lay it on a hard flat surface and bump all the bolt holes back flat. I had this problem and thats what fixed it for me, someone had over tightend them at some point causing them to flare the pan around the holes. Easy enough to fix but no way will it not leak until you get it flat. I also like to hard rubber gasket.

[Myself]

I agree to make sure the pan is flat, I have seen warped ones. Also a good idea to hammer the holes back flat. I personally clean everything off with a wire brush. Then wipe down everything with alcohol and paper towels. Then i smear a light film of grey Import Gasket Maker (Versa-Chem) on each surface the gasket will be between. Never had any leaks this way... NEVER!!! Also the pan bolts only tighten to about 10 ft. lbs.

[cdowns]

yes over tightining number one cause of pan leaks both tranny and oil

MAXIMUM 15ft/lbs which is not much more than finger tight

i prefer replacing the pan , NOT with a cheapo piece of crap chrome one either// if the holes are indented its less than 50% that you can knock them straight the metal has a memory and once damaged they usually return to the way they were and leak shortly after install

[RicksTrucks]

hijack - My son's truck has a similar problem. We changed the gasket and now it leaks in the upper corner on the passenger side where there is no bolt. Any ideas?