I've search and found a lot of information concerning the "grinding" noise associated with the hubs, vacuum, and the IWE solenoid valve. I have replaced the solenoid valve and still have the noise on the passenger side only. While the truck is running the driver side spins freely with no noise. While in four wheel drive, it does not make the noise. Can anyone recommend my next step to determine what my problem is?

 

I should have noted, the truck is a 2006 F-150.