97 dodge 4x4 front wheels not engaging

when i shift into 4 high or 4 lo my front wheels do not engage and the light on the dash doesnt indicae that it is in 4 wheel, when it is in 4 lo the gear ratio does change but it is in 2wd still?? i think that would indicate my transfer case is working ? could i have a problem with the transfer case or a shift motor problem?? im stuck on this one thanks.:banghead:
i dont think i have any problems with my vaccum lines and it looks like the electrical wiring is only for the 4wd light on the dash, I think its just the vaccum shift motor but maybe opinions from others on this would help me with this thanks

If i's not mistaken, this is a vacuum locked front diff. If you look underneath the vehicle in the front diff you will see 2 vaccum lines and a connector. The connected has a switch that tells when you are in 4 wheel or not, try and jump the switch and check you 4whl light. you need to check vacuum at the front whheel drive actuator when shifted into 4 wheel. 1 side will be vaccum in 4 wheel the other will be vacuum when shifted into 2 wheel drive to move the locking gear back and forth inside of the diff. I would also check the main vaccum line going to the vacuum switching valve on the transfer case and in the engine comparment