I have a 65 mustang with a transmission leak. I replaced the rear trans seal and the transmission pan gasket twice. I could of sworn it was leaking out of the pan gasket but now I believe it must be coming from above the trans gasket and just collecting and dripping there. It collects on the drivers side of the transmission and leaks right at the rear corner of the trans pan. It only leaks when drivin. I can run the car for 30 minutes in the garage with nothing and the minute I take it for a spin around the block it leaks like crazy. Its a pretty constant drip. This think is just driving me up the wall now. Any ideas?
Thanks.

 

Tranny fluid is thin so when you drive it gets blown everywhere. Just an idea...my pan was leakin on my C6 so it took the stock pan off and it was warped. Bought a new thicker steel pan in hopes that it will fix the leak. Also, do not over torque those bolts. 12-15 #ft. is all you need. And also, until you shift into either R,N,D,2,1 the fluid basically stays in the pan. Block your wheels, put the car in neutral, then check for leaks.

 

Clean up the tranny as best you can with carb cleaner and rags, then block the car up, put it in gear and have someone press on the pedal while you visually check for leaks.

 

I had something similar with mine after I put the new C4 in. It seemed to me that those bolts on the pan needed tourqued a few times after the car ran a bit. I torqued them to 20lbs and after driving it almost all the bolts needed tightened again. The first tightening slowed the leak down, and the second stopped it (at least I hope it did). Maybe the gasket needs to warm/cool to fully seat, I don't know for sure but this was my experience.

 

I am having the same problem. I have put a new gasket on 3 different times. I make sure not to over the tighten the bolts ( use a torque wrench), but the damn thing insists on leaking. GOOD THING THE NEW T-5 IS ON THE WAY!!!