I had the same problem with my 92 what I found was the pivot point on the shift linkage for the xfer case (where it mounts the transmission) gets bound up its made of white metal has a steel torx bolt through the center & plastic bushings inside.
If you continue to force this peice it WILL break (I broke 2 of them) spray them down with a good lubricant (not a penetrating oil) if all else fails remove it from the truck & gut it then put it back in. Now don't get me wrong gutting it will make it very loose but its a better option than replacing it after you break it.
BTW if I remember correctly ford wants about $180.00 for the part
Hope this helps
Good luck
