I have an 04 f150 fx4 and I am having problems with the 4x4 engaging. At least I think that is what's happening. When I turn the electronic switch on the dash on the light comes on. When you start driving nothing happens, the front wheels aren't spinning. When you put it in reverse and start backing up it starts to work but then there's a loud pow sound and then it stops working. I think the reasons for this is because the man that owned it before me never used the 4wd since the man was old and never drove it at all hardly, but I was wondering what needed to be replaced or fixed or greased under there.

 

Search for IWE replacement and 4WD solenoid.

Tons if posts on how to diagnose, troubleshoot, repair and necessary tools & part numbers.

I have a write up on my IWE replacement - look through my posts.

Good luck