I have a 99 dodge 2500 cummins. When I pull the stick in 4x4 my truck is not going into 4x4. The front drive shaft is locking in and spinning but it is not doing anything at the front axle. The 4x4 light is not coming on either. Any idea what it could be. Could it be the hubs. I looked I only can find one vaccum line that comes off the axle and it is hooked up and looks fine. Any help would be great thanks.