I work with UAVs so it pretty good but i got thinking, i had read that if you disconnect that relay and drive it and you can narrow down if its electrical or mech. So i think thats were the P1765 came from.
nope a contractor. Well with disconnecting the relay threw the codes and the battery got disconnected to clear the codes and my ole man drove it around and did the ignition test again and they didnt come back.
the manual lists 3 likely causes of this issue- Rev and low gear only.
1) the relay circuit - that was my guess, anyway easy things first
2) valve body malfunction - you claim its a NEW VB - so eliminated that -
3) Front Servo/Kickdown Band Damaged/Burned... not so easy and another reason to DBL CK #1
Remember, OP, you aren't manually shifting actual gears or even all the control valves. You are shifting that range switch that is an input to the PCM. If the PCM has inputs for both P/N and a driving gear, then it gets very confused. You are lucky it moves at all.
Whoa! Many times those switches are adjustable, and need to be adjusted when installed. Let's give more folks a chance to chime in.
Edit: besides, that code doesn't mean the switch is bad, it only indicates that circuit is giving bogus input to the PCM's CPU. Could be a connector, wiring, PCM, the switch... or the switch adjustment.