1993 Jeep Wrangler 4 WHEEL DRIVE

There is a Vacuum pod on the passenger side of the front axle. When the 4wd is engaged vacuum is sent to this pod and engages the front axle. It sounds like you are going into 4wd in the transfer case but not at the axle so check this first. This is also where your sensor is that turns on the 4wd light. Is that working? There is an electrical connection just up from the axle that sometimes gets unplugged just trace it up to check. If you have vacuum at the pod or if your model is electric the pod can be bad. Hope this helps.