I have a 92 F150 4X4 AT 5.0 with 145k miles only owner. My truck will occasionally not move in reverse. It has don't this a few times. Once in my garage I could here the transmission engage but the truck won't move. I increases rpm and the truck finally clunked and then rolled out of the garage like normal. The same thing happened at work 20 miles later. I pulled it in the shop at work, jacked up the rear end, chocked the truck and the put it in reverse and the transmission engaged and the rear tire rolled. I shut it off crawled underneath the spun the rear drive shaft by hand. After a few rotations again the truck jammed in Reverse. I checked the rear break drums, they were fine. The location of the jam seemed to be in the rear of the transfer case. I lowered the the truck and tried again and the truck backed out fine only to jam again 20 ft later. I tried engaging the ESOF and that didn't help. The 4H light came on but the truck was still jammed. Eventually it again worked. When I tried to engage 4H the ESOF light didn't come on. I think there is something wrong with the transfer case. That is where it is making noise. I recently installed a new MLPS thinking that might be the problem but it was no help. Any ideas anyone? Shift motor??? Please help

 

"jammed in reverse"?? Seemed to engage reverse, but driveline could not be moved? Then somehow "unjammed", and could be moved forward? You may be right: broken shifter part in transfer case, allowing lock-up to occur? But why only in reverse? Possibly broken part in transmission.

I would yank out the transfer case, see what happens when shifted into reverse (and other gears) with it removed: if normal operation, then problem ain't in transmission. At that point, tear apart or replace transfer case. It is not all that heavy or difficult to remove. impish