I have an intermitent grinding noise coming from the front end of the truck.  If I slow to 10 mph is may to away;  if I turn on the 4wd I hear a ‘thunk’ and feel a mild bump and the noise goes away.
 I searched the web and found a similar problem resolved by changing the IWE Selenoid - theory being issues with the vacuum.   This minimized but did not solve the problem.  My dealer has not been able to solve the problem … any ideas?