My 08 F450 w/4:88's has a slight vibration which I noticed from the first time I drove it. When you maintain 51-52 mph and again at 58-59 mph, I seem to notice a slight vibration that is difficult to determine where it's coming from. Anyone else with an 08 notice anything similar?

There is also, which may be related, a noticable rear diff. whine. This whine is at varying speeds not really related to the range mentioned for the vibration. Here again, I've never had a truck with such a massive rear, so, maybe this whine is normal??

 

The whine should not be normal, and the shake can be caused by the rear end not being lined up right...drivetrain vibration...I would have it checked.