I took the car to the dealer to have the transmission diagnosed to confirm my assessment. Surging while climbing hills, chattering in the lower gears, etc. I was thinking bad torque converter lockup, they confirmed, probably something wrong with converter or internal issues. I'm also pretty sure that as this TC lockup issue has progressed, it's started to effect the shifting performance. Dr. Tranny additive seemed to help a little, but issue persisted and got worse again after a couple drives. Dealer quoted me a ridiculous sum to uninstall and dismantle the trans just to find source of problem. They said it would be cheaper to swap in a reman unit, which I'm inclined to agree with, since it will still be a 140k trans with parts swapped, and almost as expensive to do the repair as it is to replace completely.
Since I've already swapped a 2015 Explorer motor into this car 10k miles ago, I've decided that I'm going to do the work myself and already pulled the trigger on a Rockauto Transmission Authority unit. I'm 99% sure this is a rebranded ETE unit, since they sent me to Rockauto as one of the retailers that carry their unit, and it's got the part number they gave me assigned to it (T161645). They seem to have a decent reputation, it's got some sort of shift kit in it and it's got a 3-year warranty, so I'm fairly confident it will be a good unit, especially if I can actually get past repairing this beast and actually do some light modding (beyond the HD brake upgrade I've already done in anticipation).
Question for the pro mechanics on the forum: Being that this is a modern electronically shifted transmission with torque management and all various sorts of voodoo, is there a special learn procedure that has to be done in the ecu once the trans is in the vehicle? The dealer service manager said something about a shift control number off of the transmission that would need to be programmed in, and that they could do it if I did the swap myself. Could the car be driven over there (about a mile and a half) or would I have to have a flatbed tow it over? In other words, will the transmission work at all if the programming isn't completed, or is it just a matter of getting it to work correctly with this programming? Being such a short distance, I could even deal with a 1st gear drive over there at 5mph if I had to. Thanks in advance for any replies.