I have a '03 S-crew with the electronic 4x4 **** on the dash. It seems like the 4x4 isn't engaging consistently. Today I was on a grassy hill and the rears started to spin, I stopped and put it in 4Hi and still rear wheels spinning. I stop put and back up in reverse for a couple of feet and then put it in gear and it feels like the 4x4 kicked in with no wheels spinning anywhere. I stopped in the same field later and floored it in 2Hi and the wheels spin, I stop and put in it 4Hi and more rear wheel spin. I keep it in 4hi back up and then in drive again and it feels like it kicked in again. Anyone have any idea what in the world this could be....I'm assuming it's not a vaccuum line or it (4x4) would never work?? Hmmmmmm

 

Sounds like the front axle isn't fully engaging. Possibly a bent actuator shaft or a weak vacuum solenoid.

 

Is there any way for me to find out if it is any of the problems you mentioned without taking it to the dealer and paying major $$$$??? THANKS!