4.8/4l80e swap in my 68 Rambler. New PSI Harness with 4l80e connector and both speed sensors. 4l80e Segment swap completed correctly.
Car is in limp mode and pulled P0758 Shift Noid B Electrical and Speed Sensor.
With HP Tuners, I commanded 1-2 noid and clicks. Then did 2-3 and nothing.
Pulled the pan and disconnected the 2-3 noid. ***As Soon As you Plug it in, it clicks. Unplug it, goes off. I tested this with another known working 2-3 and same thing. They get hot when plugged in for a few minutes.
I would assume its being sent a ground signal somewhere.
Anyone had any ideas? Thank you.

 

Sounds like you've already done most of the diagnosis yourself. You've used a scanner to check. You've tried a different noid. And you've reached the likely conclusion that the solenoid is grounded somewhere.

Start tracing wiring. I would unplug the connector, find the correct pin, and check it vs ground. if the harness is permanantly grounded, you know which way to start looking. If the harness isn't grounded, check out the internal harness to the trans and see if a wire is worn/burnt and grounding internally.

Let us know what you find.

 

Sounds to me like either the harness or the PCM wasn't done correctly. If you plug a 4L60e plug into an 80e and try to run it, you get this problem.

 

Issue found. The used PCM I used for the swap was bad. Something in it was grounding out the shift noid in the trans. Replaced and licensed another I had laying around and everything works perfect.

Never seen a PCM go bad before.