I bought a fairly used 2000 dodge 2500 5.9 cummins and drove it home. On the way home it started popping out of 2H and tried it in 4H and did the same thing. Got it home barely now it won't engage into the high gears at all but 4L works fine. Took it apart and not a drop of oil in it, the small range for was shaved down to nothing. Replaced it and looked over everything and looked good. Put it back in and still no high gears.. Any ideas??? Transfer case is an NP241DLD

 

that transfer case is junk anyway and has no place in a diesel truck.

swap it out completely for a NP241DHD

junk yard or rebuild shop will be your best bet. make sure it has ATF+4 in it.