Originally Posted by Never_Evil
2003 fords do not have traditional hubs.
Is the ABS light "on" on the dash? If so, you may need to replace the unit bearing assembly on each side.
There is also a set of relays that must click on to engage the 4wd system. Check the relays and electrical.
I don't know much about newer 4wd systems, but you can hear it click. As far as the ABS light goes I'll have to get back to you on that. I just doesn't seem like the front end wants to lock in for some reason.