Just one other possibility....AfterI had my transmission done I had a similar problem. After the new trans and cooler normally my trans temp would never get over about 140 or 150. Well, I was in a small group of fellow PSD's running late to a NHRDA event and was running about 100mph down the interstate. Stopped at a gas station and noticed fluid pouring out of the transmission and dripping off the rear end etc. One of my buddies commented that he was wondering what was all over his windshield...lol. Anyway, long story short, it was leaking from the dipstick tube at the transmission. With the deep pan and an apparently over full transmission when it heated up it expanded enough to be above where the dipstick went in. (At least I assume that was what happened). It only did it once more after that (When the trans was up around 160 and it hasn't done it since. (More than 2 years have gone by with no other problems) Transmission still hasn't seen over 160, but I suspect if it ever got to 200 it would be leaking again. Just another idea to ponder if it all seems good after a refill.
-Aaron