Driving at a lower speed, like 15mph, I figure in 2nd gear and hear a loud bang from the back of the truck.

I stopped the truck and parked it to check the sound, and nothing looked out of the ordinary, and nothing was run over, etc.

The truck was running the entire time while in the park.

I put the transmission in the drive, and it would not move.

I turned the truck off and back on, but it still wouldn't move.

Then put it into Neutral and Drive, which drove fine.

I went to the store, put it into the park, turned it off in the parking lot, started after shopping, drove perfectly normal all the way home up some significant hills, and stopped driving maximum speed of about 35mph.

It sounds like e transmission input shaft to me.

The truck does not move freely in the park, and the truck has a BD protect68 and TCM tuning with NO CEL.

It is a factory 2012 valve body and 68RFE.

Any help is greatly appreciated.

Thank you.