Well i have a 2004 Ford F-150 xlt 5.4L .1st i thought it was maby a vacuum leak. but then the noise got worse. so yesterday i took off the wheel, caliper, and rotor. i spun the hub while truck was running and cv did not move, like it suppose to. But only when i drive in 2wd the noise is there as soon as i hit the gas or even when im coasting. ANY ideas i will take. iv tried everything i know about it and still makes the noise. my guess the 4x4 is not fully disengaging in the front driver side tire. but I'm an HVAC/plumbing mechanic. not auto.

 

sounds to me like a bad IWE on that side. if it stops when the 4x4 is engaged, then chances are this is what is bad. search for IWE replacement on here.......