This happened on my '82. The problem was that the detent system that keeps the rails from just moving around had gone bad on the 2wd/4wd side. Using the stock shifter (J pattern) I experienced no problems while riding around in 4Lo, because of the interlock that kept the 2wd/4wd rail from moving while the H-N-L shifter was in Lo. However, when I rode around in 4Hi, the 2wd/4wd rail would slip into 2wd, so now my shifter is sitting in the 4Hi position on the H-N-L rail and the 2wd/4wd rail has moved to 2wd, so the shifter was stuck in 4Hi and the tcase was actually in 2Hi. It took me pulling the shifter and driving around a field actuating the shift rails with a screwdriver to figure this out. I temporarily solved it by not using 4Hi at all. I eventually put a twin stick in to solve it until I put my MC07 in.
