what year did ford install the disengagement system that allows the wheels to be unlocked in the hub. I just watched a yahoo video put out in dec 07 that shows the half shalf axles not rotating with the wheel until engagement occurs.

here is the link.
http://video.search.yahoo.com/video/...d=000163756402

 

Prior to 97, there was a hub that locked and unlocked, either manually or automatically. 97-03 and the 04 Heritage locked and unlocked at the diff. 04 up have IWE's (hubs), that have a default of locked, and unlock by vacuum when in 2wd with the engine on.

 

I have an 06 and didn't know about the hubs. I feel much better knowing the axles aren't turning while driving. I have the AS 2 lift. I have also seen many used 04 and up f150 on car lots with busted cv boots and grease leaking out.

 

Many of the problems with the cv boots having a problem are caused by the leveling kits. Not sure it is all, but at least some.