2021 Ford F-250 SD suspension problems

The truck has has a vibration from the rear of the vehicle coming from either the drive shaft or within the rear end assembly. The vibration begins at 67 mph and goes away at 70 mph, comes back at 72 mph and goes away at 75 mph and then comes back at 77 mph. I have not driven the truck beyond the third vibration speed. My concern is that something mechanical has a problem and there is no way to determine when and to what degree it will fail.

The contact owns a 2021 Ford F-250. The contact stated that while the vehicle was at the independent mechanic for routine maintenance, the mechanic informed the contact that a small amount of fluid had leaked from the front differential. Additionally, the contact stated while driving at various speeds, there was an abnormal metallic and whining sound coming from the front driver's side of the vehicle. The local dealer was not contacted. The vehicle was not diagnosed or repaired.