Auto trans leak after gasket change !

[86redMed]

Hi everybody,

when I bought my car (4 month ago), there was a little leak from the transmission. After a small cleaning, it appears that the transmission oil pan gasket was cracked.

Well, I've changed the filter and its seal, clean the oil pan and gasket surface and put a new gasket and it is still leaking !!
I have thighten the oil pan bolts at 96 in-lbs like it is said in Haynes manual. Is it the good torque ? Chilton says about 15 ft-lbs...
Does this transmission (late 1986 TH700R4) needs a sealant on the gasket ? Or is it another problem (oil pan deformation, another leaking point, transmission gasket surface deformation)?

I need your help and your precious advise guys !!!

[BigRed]

What type of gasket did you use? Silicone, Cork, Flexitallic?

Ive found the cork ones are decent MOST of the time and when they still leak (Could be from hairline grooves in cork) you can just use a Silicone gasket sealer then put your cork on it that will usually solve the probelm (AKA Gasket in a Can)

I like the use rubber or silicone gaskets (If I can with a steelcore) these like NEVER leak unless theres a imperfection on the pan (Dents scracthes etc..) or the surface your trying to cover (Block, Tranny, Diff Cover)

As for the torque I don't usually use a torque wrench here (for Tranny pans) I just use a 3/8's rachet with a 4" extension and tighten till its snug then 1 more turn or so till its tight.

Trick is with these pans is to try and install the bolt in a star pattern the best you can (Im a Pipe Fitter this comes natural LOL)
Kind of like the way you put on a tire 1,3,5,2,4 just do that on the pan for EVEN seal If you tighten one side then the other you'll create what we call a WEDGE seal which will most likey leak.

[c4ever]

86 Red,
Boy can I relate to your problem. I've done my 82 (same tranny) 3 times with every different gasket known to man. Still leaks In fact I'm about to go in for a 4th time One things for sure, I got some clean tranny fluid. I don't recommend any sealers or gasket treatments. On the 85 no leaks. "Go Figure" I'm at a point where I'm tempted to use a gasket sealer. 15lbs is the correct torque and you do need to tighten in a star pattern. Make sure surfaces are clean of old gasket meterial.I hope you solve your leak and let us know. If I succeed the 4th time around, you'll be the first to know.;stupid

[Edmond]

The same thing happened to me the first time I changed the tranny fluid. It leaked towards the rear and I couldn't figure out why. So I did it again, this time with much more care and I used some gasket sealant. It's some orange stuff that smells terrible but I think it's done the trick because I don't have any leaks. BigRed is right about that pattern though. Don't ever just go all the way around in that clockwise/counter clockwise pattern. I was also told not to do that with your lugnuts on the wheels either.

[86redMed]

Well, I juste use the gasket given by ACdelco in its package (with the filter). I don't use any gasket sealant because it is not written in the books but, I think it is a good idea (much more if tis the soultion !!).

I will try all your advises. Now, I've got the correct torque so, it will perhaps stop leaking.
I was afraid of overtightening because I broke a bolt (my father give me a bad torque: 20 ft-lbs) so I took the smallest given by Chilton Manual.

[Paul G]

I just put my overdrive pan back on with no gasket at all. Used silicone sealant only. The local Chevy dealer said he cant get the gaskets anymore. They just use RTV. So far I have no leaks.

I would use a little RTV on both sides of the gasket every time. It's good insurance for avoiding leaks.