trans has enough new fluid (freshly rebuilt), no check engine lights, new TCM, multiple new solenoid packs and multiple new valve body’s, truck goes in reverse and acts normal, but in drive it’s hardly moving even with the peddle pressed half way down, after a minute or so the switch from neutral to reverse is really rough, buzzing noise from transmission, i’ve been battling this for months now and still have not the slightest idea of what it is, does it need a relearn procedure?? do i need to test all my wires in the harness? i’m exhausted but i desperately need a vehicle to drive, any help is greatly appreciated, it started doing this after i made the mistake of putting new fluid in a trans with 100k+ miles, that’s why is freshly rebuilt

 

Who did the rebuild?

 

a guy in a town next to me, he was a rebuilder for a dealership many years ago and now does it on the side, i’ve heard many good things about him, but before a few days ago i didn’t have a scanner bc i didn’t think i needed one because the truck will show any codes, but i put a scanner on it and it showed a Po750 code, so i’ve been through multiple solenoid packs so the only thing that could be causing the problem is one of the wires in the harness because they did get wet and the truck sat for 2+ years, and the problems started before i got it rebuilt EDIT: it also got a new TCM, no other codes

 

Gonna have to inspect that harness then..... I know on the older trucks, wires liked to pull out of the connector down at the trans..... a bad connection at either end would likely set the code.