My 4x4 truck is lying to me...
 

I've got a 2003 4x4 with the rotary dial switch. When I switched it to 4x4, the light came on, I heard the three clicks, but when I started driving up the driveway (there's still snow and ice on it, it's Alaska), my rear tires started spinning on the ice, nothing from the front. I backed down, turned the switch back to two wheel drive, then back to four, heard the clicks, and the front tires still wouldn't engage going up the driveway. I then put it in neutral, switched it to four low, and it was still in two wheel drive, but it did switch it to low gear. I'm guessing that the engagement motor in the T-case isn't functioning properly, but I'm not sure. Anyone familiar with the workings of these things and could you give me a few ideas as to what could be causing this. Since it's the weekend, the service shop is closed. Thanks.

The transfer case is working properely if it went to low range. Your problem is going to be one of mulltiple items. These are a bad engagement solenoid, a vacuum leak in the line from the solenoid to the front diff, a bad vacuum motor at the diff, or the fork that is driven by the vacuum motor is broke.
The solenoids are on the firewall, passenger side near the hood mount. One engages the front diff and the other disenages the front diff. Off the top of my head, I can't remember which is which. Someone will chip with the arrangement. You might try swapping the vacuum lines and see if putting it into 4x4 and back out and see if you now have 4x4. If so, the engagement solenoid is bad. If not you will have to look further.

Edit - One other thing I have heard of is that if you have been mudding that mud will cake in around the vacuum motor so that it can't move the fork to engage the diff.

You wouldn't happen to know where that vacuum motor might be? It is breakup around here and I have to drive through silty slush from time to time. Thanks for the quick run down of the system, kingfish51, kinda wishing my truck had the manual T-case shifter like my Bronco does.

The vacuum motor sits on top the diff. And it wouldn't matter if you had the manual shifter. The front diff still engages the same way. There are no hubs to engage, so it is all done at the diff.