Sealing Transmission Pan

Good Afternoon,

I searched for threads for sealing transmission pans. I have an FMX that will stay sealed for while, but eventually start leaking again. I have straightened and even replaced the stock pan. I know there are some wizards out there that could provide some of those unlisted techniques in providing a long last sealing solutions to this issue.

Thank You

mustanng7173

You do not use any sealant on transmission pans.

Good Afternoon,

I searched for threads for sealing transmission pans. I have an FMX that will stay sealed for while, but eventually start leaking again. I have straightened and even replaced the stock pan. I know there are some wizards out there that could provide some of those unlisted techniques in providing a long last sealing solutions to this issue.

Thank You

mustanng7173

Click to expand...

I would expect you to get several responses on this but here is one. Assuming the sealing surfaces are flat and smooth. Also assuming there are no cracks in the thread bosses caused by someone applying rtv/goop to the bolts and hydraulically causing the bosses to crack. Use the black rubberized gasket, clean the sealing surfaces with lacquer thinner, clean both sides of the gasket thoroughly with lacquer thinner. Put in place without contaminating anything and torque fasteners to spec in at least two steps. Heat cycle and re-torque when cooled. It has always worked for me, same with valve covers. Just one approach. Chuck

I fought this on my '72 where I had never had this problem before on several early Mustangs. On this car the second time, I pulled the pan, cleaned everything far better than I ever have, then spent 20 minutes with a hammer/dolly/level getting it as dead straight as I could. Then I used weatherstrip adhesive to glue the cork gasket to the pan and carefully installed it not over tightening.

I see you have a new pan, so as C9ZX suggests, look for irregularities or something broken. There has to be an issue, mine was the pan was too bent up from over tightening. Good luck as I know how frustrating chasing this problem is.

Hello To All,

Thank you for the responses. I will try the recommended solutions listed above.

mustang7173

Automatic and CLEAN go hand in hand. If you go to a transmission shop and do't see stainless very clean tables, move on.

I had the same problem on several transmissions of different cars with cork gaskets.

I changed to ATP fiber gaskets, attached them with a very thin film of a non-hardening sealer like Curil K2, bolted the pan to the trans and torqued the bolts.

Never had a problem again.