Hey Gang
I had an issue with my 4wd this week on my '06 F150. I flipped the switch to 4 hi and nothing, no sound, no lights, no nothing! I spent a pile of time reading on here with several good suggestions to try. My neighbor is a Ford dealer mechanic so I asked him as well. The first thing he wanted to know was if I had tried to go into 4wd above a speed of 80 kph, which I had. Apparently the '05 and above have a "protection" system on the 4wd. If the truck feels what your trying to do will damage the drive line it will trip the breaker controlling the 4wd. I simply removed the negative cable, there by resetting the breaker and now every thing is good. I guess this protection system is not to widely publicized but does exist. I hope this may help some of with a similar issue.

Thanks for all the great threads and help.
Paul

 

That's news to me. Thanks for the information!