That IS the culprit.
Had the same thing happen on my 97 ctd 4x4 dually. 4wd stopped working on my way out of a particularly nasty trail on the hunting property. I managed to claw my way out by putting it in 3rd gear and just letting the dual rear wheels eat.
When I got back on solid ground, I looked and the vacuum line had come off at the tcase. Put it back on, and voila, 4wd worked again.
1996 Cherokee Sport 4x4
1988 Cherokee Pioneer 4x4
Last edited by TRCM; 08-27-2012 at 07:26 PM.