I have a 2005 f-150 STX 4x4, and have had problems with the 4x4, its not fully disengaging. The front end will grind if I attempt to use 4x4, and it will jolt when slowing to a stop when in "2 wheel" like the 4x4 driveshaft is turning and trying to engage. I replaced the vacuum lines today, but nothing improved. Any suggestions? Also, I am very new to this site, so I am not entirely sure if this is the best forum to ask questions on, but any help would be GREATLY appreciated.

 

This is the most used 4x4 trouble shooting thread.

https://www.ford-trucks.com/forums/836438-everything-you-wanted-to-know-about-the-iwe-system-and-then-some.html
If the grinding is occuring when IN 4WD then there is likely a worn (maybe both) wheel hub. The IWEs may also be worn out.