I have a 2000 F-250 Powerstroke with electronic shift on the fly 4X4 but when I switch it into 4X4 the hubs do not engage unless I get out and manually lock them. Any ideas on what the cause of this might be and how to correct the problem? The 4X4 engages and low range also kicks on but the hubs will never lock in with out the manual engage. I think it must be a damaged vacuum line but am not sure. If that is the case anyone know what it costs to fix? Any help will be greatly appreciated.

 

Could be a vacuum leak, could be that your vacuum pump is not working. I for one would check to see if the pump is working. Secondly, if the rotors have been off the the axle's there is good possibility that the seals in the hubs were damaged or not replaced. If that is the case the chamber won't hold vacuum and your ESOF will never engage the hubs. Did you ever have any brake or bearing work done on the front axle?

 

I just bought the truck a few months ago and they said they went through everything and looked at the hubs and rotors. I would assume that means they took them off and inspected them. I trust dealers about as far as I can throw them so I bet they didn't get the seals back on right or damaged them in the process.