Mile-O-Matic / Ford-O-Matic 2 Speed Transmission Leak Mystery

['59Edsel]

Hey everyone, I have a 2 speed Mile-O-Matic / Ford-O-Matic / Merc-O-Matic / Cruise-O-Matic from 1959. Just yesterday after running my engine, getting it hot, and running though the gears ford good measure, I noticed a small but steady leak coming from the rear of the transmission. I stopped the engine and investigated. I had just the from of the car on jack stands from this point. There was a good amount of fluid around the pan and its bolts, but it appeared to be coming from the reverse servo cover (driver's side servo cover) I wiped her down and decided to wait until today to see if anything else had seeped. Well, I get under there to look earlier and everything is pretty normal, not dry but nothing out of the usual for this tranny. Maybe just a little seepage from that serve cover. So I decide to jack up the rear end and run her in the air. I start her up and put her in reverse and I get a huge overflow out of the filler tube. I shut her off and wipe everything down / do a little online research / look in my Ford-O-Matic manual and see that causes of this are: aeration of the fluid; coolant in the fluid; and a blocked vent tube. Well, aeration I guess could be a factor. I did just recently do a complete fluid change on the tranny along with a complete empty of the torque converter. But I dunno. Coolant is a definite no because I have an external cooler. And blocked vent is maybe. I eventually did locate the vent tube and cleaned it up with a rag, seemed ok. So after all that, I start her up one last time, all while in the air, and let her run through reverse / drive/ neutral / low / and back to park. I don't get any more overflow through the tube, and that small but steady leak kinda disappeared. I'm going to do a little more investigation this weekend, but I wanted to throw that out there for now and get your guys opinions. Thanks in advance for the help everyone.