2003 Chevy Silverado: Shifts from 2wd to 4wd, 4wd to 2wd, and 2wd to neutral at low speed or start up on its own. The problem started two years ago when it switched from 4wd to 2wd. I was able to put it back into 4wd only after I shut the truck off for 10 to 15 minutes. About six months ago it went from 2wd to 4l several times while driving at low speed. It reset on start-up after a prolonged shut down (this always happened during snow or wet conditions). Lately it shifts from 2wd to neutral. This happened once at low speed and once at start up. Again, it would not reset immediately after shutting down the vehicle and restarting. I had to wait for 15 minutes or longer to restart the vehicle for it to reset. Any help would be greatly appreciated. I would like to fix this before I have to call a wrecker to the middle of nowhere because I'm stuck in 2wd and can't get out of the woods. Thanks.