Leaky Transmission with Good Seals?

My Mustang has been in my garage for over four years with both engine and transmission out. The engine on a stand and the transmission on the floor. I recently sent the engine out to be rebuilt. When the engine got back, both the rebuilt motor and the transmission were bolted back together. Now, keep in mind that the transmission was rebuilt about a year before I parked the Mustang in the garage. So, that makes the rebuild for the transmission about 5 years ago. Everything seemed to be coming together quite nicely. I got the engine up and running and idling smoothly. All with no fluid leaks. Well, that’s what I thought.

When the car is put into reverse or drive transmission fluid comes from the bottom of the bellhousing. Mind you, this does not happen when the car is in park or neural. Thinking that the front seal was damaged, I disconnected the transmission and replaced the seal. The problem was that both the new and old seal looked identical. There was nothing wrong with the old seal.

I have done a little research and come up with two possibilities. First, when put in drive, pressure is building up in the transmission and forcing the fluid past the seal. Meaning that there is some sort of relief valve clogged? Second, I thought that maybe the pressure plate could be bent and causing the shaft of the torque converter to wibble wabble in the front seal causing it to leak.

Any ideas?