I have a 2004 LARIAT 4x4. I will be driving at any speed and all of a sudden a loud grinding/whistling noise will start coming from either wheel or both at the same time. It will go away as soon as I slow down to under 5mph and then I will feel a clunk and then no noise. It comes and goes and isn't a constant thing.
I think it is the hubs trying to lock in 4x4 but I'm no mechanic. I have recently learned that when I hear it I turn the switch to 4x4 high and the noise instantly goes away.
Has anyone had this issue?
And or anyone know for sure what it is and what needs to be done to fix?
Thank you very much for any help.

 

Check and make sure you have the updated IWE solenoid on the firewall right behind battery, it should have a rain shield on it. If you dont i would get the updated one and see if it fixes it. If not its most likely your IWE actuators tryinf to engage/half engage causing grinding. There is a few tsbs on this

Just had to replace both actuators.

Rockauto is your best bet

 

If you have a vacuum pump, you can test the solenoid as well as the one-way valves. If one of the check valves is bad, go pay the extra money for the Ford part, as the Dorman cheapies are slightly smaller and will not hold vacuum with the original hoses. As I learned after 2 days of checking and rechecking everything with the $5 Dorman parts.