First of all, there's nothing wrong with the motor. On a second gen, the motor is only used to shift from 4auto/high to 4 low. Engaging of high is only a matter of energizing the transfer case clutch in the transfer
The first thing I would look at in a '95 is whether or not the front driveshaft is engaging. To do that, put the truck in the air on jack stands, start it up, select 4auto, then get out and see if the front driveshaft is turning like it should. If so, we can eliminate the transfer case as the problem. If the front d/s does NOT turn, the problem is in the transfer case, or in the wiring going to it (specifically the brown wire somewhere between the TCS relay and the transfer case clutch coil.
Now, assuming the driveshaft turns, on a '95, I'd look at the center-axle disconnect. There is a vacuum solenoid that engages/disengages the front passenger side axle to and from the differential. The lines can crack and leak, the actuator can freeze and/or break, and the and the solenoid can fail to switch when it should, not applying vacuum. This is IMHO the most common problem with the '95 and 96 systems. (The '97-03 F-series have a similar problem with their front axles as they use a similar setup on the front axle) To fix it, you need to start at the solenoid and see if it's changing state, check the vacuum lines for leaks, and check to see if the actuator is moving in the diff.
Hope that helps! Let us know what you find.
-Joe