I have a 1997 dodge ram truck. When i lock it in 4x4 it will work as long as the truck gets in no bind. If the trucks gets stuck or go through sand it will slip out and will not work at all. A friend told me that it is either the vacum line or the ransfer case. When i take out of 4x4 i can hear the gears grind so i now hat it is engaging. Anyone got any ideas.