My 06 F-150 has a loud howl (like mudder tires) when foot is off the throttle. In the last year I have had rear diff clutch packs, all diff bearings(2 pinion and 2 side) all replaced and now this load howl. The second I use the throttle it stops.

Has anyone experianced these symptoms?

 

Why did you have all that work done? Was it noisey before? How many miles on the rig? I haven't experienced this, but I remember from auto shop too many years ago that, that is a problem with setting up the way the pinion gear meshes with the ring gear. If it's set up wrong one way it will do what you describe and if it's set up wrong the other way it will howl on acceleration and go away on deceleration.