For 03F150Man:

OK, I have finally had a chance to check out your suggestions. First, to answer your original questions, the truck is a 97 Supercab with a 4.6 V8 and Overdrive transmission. Never wrecked, shocks have been replaced about every 22,00 miles. Front bearings are relatively new as are the rear wheel bearings and the differential bearings.

The vibration/noise starts at 1,800 RPM, (58 MPH) when in overdrive and remains until about 63 MPH or just over 2,000 RPM.

I disengaged the overdrive and tracked it on a smooth newly surfaced roadbed. In 3rd gear, the vibration starts about 2,800 RPM, still at roughly 58/59 MPH. I noted that he vibration has a different frequency at 2,800. Any new thoughts?