4X4 DONT WORK

[F-450 HOTSHOTER]

I have a 2006 F-250 and i just tried to use 4x4 for the first time in this truck earlier today. I turn the swith to 4hi and the 4x4 light comes on but it still only spins the rear two wheels. I tried 4low and the same thing happened. The 4x4 low range light comes on but only the rear two wheels are spinning. Also i switch the 4x4 on and my ac switches to defroster and after a little while it switches back to normal lol. I dont know hopefully some one can help me with these issues. Thanks....

[strokinpower]

you have a vacuum leak. Get out and manually lock the front hubs

[jdman49]

sounds like either a vac. line but could be a bad hub i just replaced my stock hubs with mile marker manuel hubs becaus one went bad an it was cheaper to replace them both than 1 oem hub

[Country Mav]

Where are the vac lines located for this? Mine is doing the exact same thing. It has NEVER failed to lock in until the other night. Really left me in a bind. Can y'all shed a little more light on it for me?

[jdman49]

i didnt waste my time looking i didn't like my factory hubs i wanted manuel ones so i never got let down again.

[Country Mav]

Found my leak. The passenger side hose had gotten against my down pipe and melted in two. Works like new now. FYI- A WD-40 spray hose and some electrical tape will fix it temporarily and get you out of a bind...