OK - My truck has let me down for the first time. I am looking for some feedback on what the issue might be.

I have a 2002 F-150 Super Cab FX4. My transfer case is the electronic shift with the switch on the dashboard. For the past 6 months or so, my truck would not lock into 4wd low-range. The dash would show it in low, but it would only go into 2wd hi and 4wd hi. Every once in awhile, I would be driving down the road and the transfer case would pop into neutral or in between gears. The speedometer would spin just like the back wheels were off the ground. The transmission would also shift gears when doing this. To get it to lock back into 2wd hi, I would just play around with starting the truck, shutting it off, shifting the transfer case from 2wd hi to 4wd hi, and back. I would also play with different combinations of Park, Neutral, Starting it, Shutting it off, 4wd, 2wd, etc. Eventually, (usually within a couple of minutes) it would lock in and away I went.

Well, yesterday, it never locked back into 2wd or 4wd. I had my wife pull me home with the Expedition. While on the ride back to the house, I would leave the truck in neutral but I played with the switch, going from 2wd to 4wd, etc. I could hear the front-end locking in when going into 4wd. So, I know the switch is good. Also, the speedometer was at 0 while doing 40mph down the road.

So, I think it is probably that solenoid switch on the back of the transfer case. Anyone else's thoughts? How much do those things cost? Can I get it anywhere except the dealer?

Thanks for all the help.