I have a F-250 4x4 with a 7.3L diesel and i get a vibration or hum
it seems to get worse after about 35-40 mph. I'm pretty sure rear driveshaft u joints are ok. and front end hubs are unlocked.
Any help would be appreciated, Thanks, Gary

 

have you rotated your tires lately?
Fords tend to feather the outside edge of the front tires, and without rotating them at least once a year they will hum and/or vibrate.
cut me and i'll bleed ford blue
edenroadmaster