I found out that my 4 wheel drive is not working yesterday and it took us 3 hours to get the truck out. I tryed changing the relays with my towing and backup relays with no luck. I'am not sure about the hubs, but I'am hoping to change them Waren manunal locking soon. I do think that it is the tranfer case because there is no "thunk" when the switch is turned.
My truck is a 2001 F350 cc, 7.3 litter with 47000 mi on it.
The 4 wheel drive was working fine not long a go. Any ideas you have would be great help. Thanks

 

I'm guessing that you didn't have 4WD even after manually locking the hubs? That is why your interested in the transfer case.
The fuse for the shift on the fly relay, and the transfer case shift motor is in the distribution box under the hood. It's location is #17...first row....third one down from the left. It is rated at 30 amps. If it is blown; then it's time to see what's shorted in that circuit. 30 amps is alot of current.

 

I just check all the fuses and all are good. Tomarrow I'll crawl under the truck and see what I do at the transfer case shift motor. I'll keep you posted

 

I am having somewhat of the same problem on my "02 supercrew. I had problems with the gem module, replaced it and then noticed recently that the 4 while drive switch would not work. I took the switch apart and ohmed out the indicator light on the switch. It appears to be blown. The fuses under the hood and on the fuse panel under the dash are all okay. Could the indicator light be the weak link? anybody? anybody? ferris?