I have an 06 250. The hub is set on auto and when I shift to 4h in the truck it doesn't engage. I have to manualy turn the hub to lock. Any ideas?
Thanks

 

Does it shift ok on the move with the hubs locked? If so, could be a vacuum pump problem. If your heat and AC are working properly (not stuck on defrost) then your pump is probably ok but your not getting vacuum to the hubs to engage them. Check the lines from each wheel back to the vacuum relay and accumulator. You probably have a line off going down to the wheels.

 

Does your heat or air work from the defroster only if so it is a vacuum leak.

 

ac and heat work fine, I will check the vac lines...Thanks

 

If that isn't it do a search in here for tons of info.