A buddy of mine has an '01 f350 4x4 and today his 4x4 quit working. He said everything has been fine till today. Tried to engage it and nothing, no 4x4 no light no nothing? He is out plowing right now, is there a fuse or relay that i can tell him to check that would be fairly easy to do in a snow covered lot????

 

Well, since the light doesn't come on you can probably rule out a problem with the hubs or vacuum system. That leaves the dash switch, the wiring, the GEM, and the shift motor.

I would check around the shift motor first. Maybe the connector got packed full of snow and disconnected or something simple like that.