OK here goes. I've just completed the fifth reseal of the tranny pan on my 700r4. It seems that once the engine's turned off, half the fluid from the torque converter flows back into the pan, and raises the ATF fluid to above where the pan seals with the transmission case. Once this happens, the leak starts.

Originally the leak was bad, so I replaced the gasket, complete with gasket adhesive. It leaked again. Second time, I tapped flat the bolt holes in the pan, and installed a rubber gasket. Yup, another leak. Third time, I purchased a cast aluminum pan, and re-installed with rubber gasket. Much less leaking, but still a leak. Fourth time I sealed the pan using only Permatex Black RTV sealant. Less, leaking than ever, but still a leak. When I disassembled this last time, it looked like I mught have tightened just a bit too much, and that where it leaked the RTV had been squeezed pretty thin. This time I resealed with Permatex, The Right Stuff, which says its recommended for ATF fluid, and is supposed to be the ultimate seal. I only tightened the bolts on lightly allowing for lots of goop left between pan and tranny.

I'm now going to give it a couple of days to set real good. Then I'll try again.

Before you guys suggest looking for cracks in the casing, or leaking from the torque converter seal, or leaking from the TV cable, or dipstick entry point. All that's been done. This time I'm keepin my fingers crossed.

Anybody else ever experience anything like this?

 

I thought mine was leaking too, but upon further inspection I found that it was the seal on the side of the transmission. It looks just like the pan is leaking because the fluid runs down and around the pan. I replaced the gasket 2 or 3 times before I found it.

 

i have always used permatex WITH the gasket, i apply a really thin layer and spread evenly with my finger. a little extra around the holes. then after youve tightened to around 15/20 ft. pnds. wipe the excess off with your finger, leaving it smooth and proffessional looking. never had any problems this way. try a straight edge on the pan and the tranny. you never now what someone may have done to your ride over the yrs.

 

i had to redo mine and the second time i torqued it to 100 inch lbs! the transmission guy who has helped me previously gave me a paper gasket and stated emphatically 100 inch lbs.... ...and it does not leak now....i didn't even use any gasket sealer.....

 

Thanks for the reply guys. I'll try the 100 inch lbs. torquing next if this, (sigh) doesn't work.

I did check seals around the pan, TV inlet, dipstick etc.. It was definitely leaking from the mating surfaces. The mating surfaces are straight. I installed this tranny, in lieu of the TH350, and the pan is heavy cast and polished aluminum. The sealant is supposed to seal up to 1/4 " gaps. But....... I never did torque the pan on. Hopefully this'll work. We'll see when fill er up again. (not real anxious to find out).

 

Check the seal around your selector shaft. I had all of my seals replaced 2-3 times (pan, input shaft, tailshaft, etc.) to no avail. Then, desperate, I dropped the tranny again, put it on a workbench, filled it with fluid and voila, seepage around the selector shaft. A good transmission shop should be able to remove the seal (it presses in around the shaft). Also have them check out the selector shaft; if it is scored, oil can seep around it. Once I replaced the selector shaft with a new one (helps to have it on its side or upside down on a workbench) along with a new selector shaft seal, no more tranny leaks.

BTW, my 700R4 came from Bow Tie. Once I knew the problem, they sent the new selector shaft and seal without hesitation.

 

Oh yeah I have had that problem, and The Right Stuff is the solution. I used it on a third attempt on a leaky tranny pan and it sealed it right up. I have used it every time ever since and have not had problems. Just make sure to torque the bolts, tranny pans only need like 8-10 lb-ft or torque, which is a lot less than you are bound to do by hand. Also, if some threads are stripped (as I have found out) then you have an entirely different problem. Good luck.

 

Had the same problem and after several gasket changes with various sealants I changed to a Moroso pan, the flanges are thicker, and I used studs to date no more leaks or chance to strip threads in the tranny case. I had a Derale tranny pan before and I checked the flanges, they showed a slight warp.... and it wasn't cheap, the Moroso pan is by far much better quality, and not cheap either...

 

I've built hundreds of automatic transmissions and I always use a cork gasket and no sealer. The sealer acts like a lubricant and causes the gasket to split and/or distort. On a stock steel pan I always the bolt holes flat and used an impact wrench to tighten. You develop a feel for how tight and never had any pan leak. You should have even less worry with a rigid aluminum pan. As the others have cautioned though, transmission fluid can travel around and down from other sources and make you think it's the pan, particularly the front pump o-ring which is notorious for leaking while sitting overnight. The front seal will almost always leak while car is running if it's bad. The shift linkage seal also leaks overnight. The only way to be sure is to carefully wipe it down and inspect it with a light after it sits for several hours. Good luck.

 

I always use a cork gasket, a thick one. There have been times when I've made my own. Also never used sealant. Never had a problem. If sealant is needed, something is wrong. Beside, it will never last like a good gasket will. Also, while reading this, my first thought was the selector seal as well. It can be difficult to tell the difference sometimes.

 

I had a similar problem with my trucks trubo 350 with leaks. What I did last time was to clean both the pan and tranny surfaces, applied the gasket and RTV sealant and let it cure for a couple of hours before I pored the tranny fluid in. This seemed to do the trick