I checked the 94 system, it's just like the electric shift I had on my 1986. There is nothing engaging the front driveline except the transfer case and the hubs. The hubs work by themselves. The one thing that always worked on mine was the auto hubs. It's very easy to test them. All you have to do lay on your back up front and grab the front driveshaft. You will be able to turn it about a turn, maybe less, and the hubs will lock. This is with the truck off, sitting still. Once the hubs lock, you can't turn the driveshaft anymore. The only way to unlock them is to make sure the truck is in 2wd, and back the truck up 8 to 10 ft.
If your driveshaft is not locking when you turn it by hand, you have a hub problem. You can most likely peek up front while you are turning the front shaft. If one side is turning and the other is not, the side that is turning is not locking.