Got good problem solving tips off you tube .I have replaced left side actuator and solenoid and vacuum lines still have problem bypass solenoid still have problem . With solenoid bypass still makes noise move switch to 4 wheel drive noise goes away did this three times .this does not make sense ! Any idea ?
2006 f150 5.4

 

https://www.f150online.com/forums/ar...then-some.html

The IWE is not fully disengaging. Vacuum issue or the IWE itself.