Oklahoma is a ways from 4x4 season but last winter I went to put my '06 fx4 into 4 high and when I hit snow/ice, bang bang bang bang! It would jerk and clank real loud, and it was consistent. Could that be a bad IWE solenoid?

 

Yes.. Located on the firewall behind the battery.. Look to see if it has a rain shield on it or not.. Newer version comes with the rain shield.