My buddy has a 2004 5.4L 4x4 with 70k miles. Once it gets up to operating temp and you are applying throttle it makes a noise, sort of a screeching noise. If you let off the throttle it stops. Their are no DTC's and the truck drives and shifts smoothly. I am thinking it could be something in the exhaust. Any other ideas?

 

Make a video, could be an exhaust leak

 

The whistle tips go "whoo whoo" !

 

That video cracks me up every time I watch it! A video would not catch it. You pretty much have to have the window down to hear it and the wind would block it out.

 

Bearings? U joint? Pulley?

 

CHECK YOUR AIR FILTER BOX FOR THE FOAM GASKET. I BET IT IS MISSING
CHECK HERE

https://www.f150forum.com/f4/bog-dow...solved-166431/