Well where to begin??? I have a vibration(humming noise) coming from under the truck. It is always present, PRND21 does not matter. When I put it in gear it seems to get worse and louder? I have been to 3 transmission shops and have ruled out anything to do with it. I pulled a few codes a couple weeks ago regarding the EGR system.ALL PARTS REPLACED! still have this noise. I also went to a muffler shop thinking it is a cloogged converter? No such luck... when in the air we put in gear and the noise intensified and could hear it through the bell housing. I am lost... any ideas?

thanks ,
2001 F150
5.4
4x4

 

Sounds like an exhaust rattle. Check for any of the exhaust hitting anywhere on the underbody.