Need some help I have a 2008 f150 xlt 5.4 and I have been chasing a 4x4 issue for some time . The problem I am having is the passenger side axle seems to stay engaged to some degree when I jack it up and the truck is in 2wd the passages axle still spins ! I have verified that my vaccume system is working and have enough vaccume to disengage . I went ahead and orders a new iwe after disconnecting my upper control arm and removing the old iwe I connected the vacuume line and verified that it was working I installed the new Ford part anyway because you never know after reassembly I still have the same issue I made sure to spline the axle with the hub correctly I engaged the 4wd and it seemed to be repaired but when I tightens the axle nut down it again will not disengage that was suspicious I then realized that the axle nut was different od 14mm instead of 13 mm I assumed it was the wrong size nut and orders the original from Ford when the new one arrived I then realized it was a different id and that must mean it’s an aftermarket cv axle I am stumped and need some suggestions ? What made me test everything even though the 4wd engages and works is a slight winding noise from the front that goes away after I engage the 4wd I assume it’s from passenger axle not disengaging also the front wheel hubs are brand new Ford I didn’t notice the noise before because I had a lot of road noise from cheap tires I have some new generals now much quieter