I just bout a used 2012 Ford F250 4x4 with the 6.7L with 100k miles. When I am on the freeway I have a loud vibrating/buzz noise that sounds like a heavy plastic piece catching wind and vibrating. The noise is only present at or around 70mph. The vibration can be felt more so on the windshield than the dash but sounds like it is coming from the center or right of center under the dash. Any ideas??