Hey guys, new here so if this is somewhere else please let me know. I have a 2012 ram 3500, couple of go fast parts and a built 68rfe. About a week ago I stopped at the grocery store to get some milk, came back out, flashed up the Truck and went to reverse out of the stall. Got about 5 feet back ( struggling like I was butted up against a curb ) and it locked up solid. No more reverse, brakes fully released and bound up solid. Put it in drive and it moved forward easily, then backed out of the stall as normal. It seemed to do it only when hot but it did it yesterday morning from a cold start. Any ideas where a guy could start? I plan I’m ripping diff and trans pans off this weekend to check everything out but if someone has had this happen before it would be awesome to know what it was.