[Bumblebeebum]

Just wanted to close out this thread with a resolution but you can still reply if you have any questions about my experience in a transmission replacement.

Diagnosis:
Took it to a couple of transmission shops and they said the torque converter was bad and probably blew chunks into the main bell housing so the whole thing needed to be replaced. They hooked up a reader and looked at RPMs or something but no codes. And the other issue (undercarriage wash, due to fuel system service was purely coincidental).

The cost of a used low(ish) mileage unit was less than the cost of a rebuild and there were a lot of shops that did rebuilds but questionable quality indicated by very short warranties. Dealer wanted like $7k for a factory reman so I went the used route, with a decent warranty.

It runs smooth as silk now.