This is a 01 F250 4x4 supercrew, 5.4, auto 50k and all stock. Driving down the e-way and out of nowhere I got this noise/vibration that is best described as if you were running over rumble strips. In fact it felt exactly like that! I was going to pull off at the next exit and then I hit a small bump in the road and it quit just as fast as it started This truck belongs to someone else and I am trying to figure this out. He told me that when it happened to him he locked both hubs and the noise quit. But the 4wd seems to engage and disengage properly. When it did finally happen for me it was pretty severe and it seemed like the whole floor resonated so I am unsure what area it actually came from.
Suspension, brakes all are in fine shape. Any idea's?

 

Wow....30+ views and no input
Anyway I found the problem. The l/f spindle needle bearings are junk from water intrusion, also destroyed the outer axle bearing surface. This would cause the locking hub to try to lock itself at times.
There is a special service message on this from FOMOCO. It is not a tsb or recall, kind of a internal bullitin.
So to fix it properly it will need a spindle(full of rust, won't hold vacuum) a hub and a outerboard end of the axle and a inner seal. ouch!
By the way the needle bearings are available separately but This one needs a hub from the rust on it.

 

Hmm... I might be having this problem also. I randomly get a front end vibration. How much did this cost to fix?