So the th350 in my Skylark won’t stop leaking from the pan. It’s been doing this since I’ve owned the car for the last 4 years. When I got the car I replaced the cork gasket with a new cork gasket- worked for a few weeks then started leaking slowly again. Then had the tranny rebuilt when I rebuilt the engine, again the pan gasket was replaced with a cork gasket- still leaked. Finally I got sick of the old pan which seemed to have a slight warp to it, bough a new aluminum pan with a drain plug from summit, installed it with a rubber gasket that came with it this time, and as soon as I took the car out for the first cruise with the new pan it started leaking after it cooled down. I’m at the point where I don’t know what else I need to do to make this thing stop leaking. The leak is only coming from the pan, the gasket for the dipstick tube was replaced and is dry, as is the speedo housing. I’ve heard not to use RTV, anyone have any other suggestions?
Are you installing the cork gasket dry? If so, you may want to try spraying the gasket with Permatex Spray-a-Gasket to make sure you are getting a good seal.
The two I’ve installed went in dry. I could definitely try that. Yes I know where it’s leaking from, it’s the same spot it’s always leaked from even with the old pan, passengers side front corner.
Does it leak from the same spot.Maybe you have a small crack in the case.If not I would pull the pan clean and dry case and pan. Use gasket maker rtv on the pan and install the gasket.Put a light coat of gasket maker on top of gasket and install.Don,t over tight the bolts or the pan will bend in the bolt area.Let it dry before you fill the trans.
Passenger side front? Have you checked the detent (kick down) cable? There is a small internal O-ring that seals where the cable sleeve slides into the transmission and bolts to the case. If you look in the Chassis Manual in the THM350 section, they talk about "case porosity" and how to use epoxy to fix that. That is a remote possibility, but if the Chassis Manual mentions it, it is a possibility.
That's why road race cars are painted light grey or white on the underside. Keep in mind that oil leaks down. I had a leak in the T400 in my Riviera. You'd swear it was the pan gasket leaking. Turned out it was the O ring on the plastic bulkhead connector for the downshift solenoid just above the pan rail.
So I did have this issue with the dipstick/filler tube leaking oil, but that was fixed and I’ve had no leaks above the pan since that. The kickdown cable has never leaked on me and I’m 99% sure it isn’t leaking now but I can definitely double check that. Is this okay to do? I thought about using rtv but though rtv on transmission pans was a no no. Also I torqued the bolts down to the recommended 12 ft lbs as in the chassis manual
On things like this I prefer the right stuff over rtv. But I will warn b4 going any farther, when done right the next time you have to take it apart will be a job. When I use it I end up getting a thin sharp blade and cutting the sealer, it doesn't come apart easy. The name of the game is clean. You have to get all the inside stuff from dripping down on the rail. Clean the pan and case with alcohol, not brake clean. Once dry put your bead on the pan in th middle of the rail. Go around all the hole fully. Give it just a couple minutes to sit, clean the case again just to make sure no oil is left. Only lightly snug the bolts....just till you see the stuff reach the edge of the pan.....you want to.make sure you can still tighten the bolts without over torque. Let it sit another 45 mins or so then finial torque........this will allow the sealer to mostly set up and act like an o-ring when you snug it all the way down This stuff holds so well I know someone who used it on the intake end rails and around the water ports......pulled a motor, got taking it apart pulled the intake bolts, got stopped, came back the next day picked the motor up again by the carb flange, moved it a crossed his shop put it on an engine stand then remembered he already pulled the intake bolts. This was an iron big block too. When done correctly the right stuff will seal and will will hold
It may not be at the pan gasket. But if it is, gluing the pan on ought to be the cure. The chain cover on a Toronado is a tough case, and some use this to solve the problem. Bruce Roe
I've chased my tail on a pan gasket and it turned out to be the seal around the pump. not the input shaft but the pump to case seal..
Today I confirmed it was in fact the gasket. I drained the pan and pulled it off. The rubber gasket was wet in both sides of the gasket almost all the way around the pan. Really not sure how that happened. I finally gave in, bought a new cork gasket from a local trans shop, and gave it a slight coating of transmission specific rtv. Hopefully it works this Time, if not I’m going to say screw the gasket and just use the right stuff
Are you suppose to run your car lightly for the first couple of day wi th a new gasket on your trans? ALSO, aren't you suppose to go back and re torque your pan bolts after a couple of days too??
This is exactly what I did with the rubber gasket. Took it out for a 10-15 minute ride, let it cool, and retorqued. Took it out the next day for a little bit longer and again retorqued. Didn’t seem to help at all, not with that rubber gasket atleast. The trans shop I bought the new cork gasket from scolded me for even installing the rubber gasket in the first place, saying they are worthless.
They are. Had to replace my valve cover gaskets soon after purchasing the car because they were leaking badly on the manifolds. Took off the covers and sure enough, the gaskets were rubber. Installed Fel-Pro cork gaskets and it’s dry as a bone.
