2001 350 4X4 auto, 4r100, previous owner replaced the transmission with a low mileage used unit (160k).
I've searched this problem and found a few members with the similar issue, but mine is a little different. Drive gear will engage maybe half the time, does not matter if the tranny is hot or cold. Have to start in 1st then bump up to drive. Took it to a tranny shop and it worked the whole time for the test drive, until I left. Pretty much flip a coin and it might work.
For some strange reason it will always engage after i back out of my driveway (slight incline) onto the most level part of the road. If I back up all the way with my back wheels off the road, taking the truck slightly off level, it won't engage. WTF.
Fluid level is fine. One member talked about a loose center support bolt, could that cause this? Opinions would help, ready to try anything before actually replacing the tranny.