New transmission but getting code P0715

[JB7795]

I’ve got an 04 Explorer 4.6L AWD that I’ve restored, rebuilt engine top to bottom (no issues there), a new transmission (5r55s) and torque converter amongst many other things like rebuilding the rear differential etc everything was going great with the truck for the past 6 months, no CEL, no engine or trans issues I’ve actually driven it from Indiana to Texas 3 times and never had an issue until last week. We were driving home one night on the interstate and all of a sudden the engine just stalled out of nowhere giving no prior indication that anything was wrong, the engine just shut off but fortunately it was late so hardly any traffic and I was able to safely pull over somewhere but the truck restarted without hesitation and continued on as if nothing happened so I thought maybe I’d accidentally pulled on the key or something and disengaged it from the ignition. Then a couple days later the problems began, driving on the interstate again and I heard/felt a clunk when the CEL came on, O/D light flashing and wrench light on. I was able to limp it home where I used my scanner to pull the codes, P0715 for trans input shaft sensor and P2106 which seems to be a generic code for the throttle going into forced limited power, there were also a couple ABS codes but I’ve had those pop up prior to this and I believe it to be because of the tone ring inside the rear diff I noticed when I rebuilt it that it was slightly worn and corroded in a couple areas but stupidly didn’t want to spend anymore money on replacing that even though I should’ve. I’m not sure if that would affect anything with the trans? I’m looking to replace the tone ring though anyways, I ordered a new rear diff speed sensor as well. I’m looking at ordering the new 3 speed sensors on the transmission because the new trans didn’t come with any new sensors, but I can’t figure out which is which. I remember when I replaced the trans all 3 sensors from my original trans looked identical but reading online it seems two of them are identical but one of them is different possibly the intermediate shaft sensor? Just looking for any insight into this, is it really just the sensors or is something else going on?