I have a whirring noise/vibration start at around 20mph quites down at 25 and starts back up at 50,I have narrowed it down to the front end as when I engage the 4wd the vibration gets worse and when I disengage the 4wd about 20 seconds after I push the 2hi button the front end makes a clunk like a bearing binding up and releasing,I am thinking that one of the hub bearings are shot or could this be a dying cv axle???I dont have any clicking/poping while turning that would indicate the joints are worn and the boots are intactbut as I said I have a odd clunk when I disengage the 4wd.Any ideas???

 

Solved my own problem turned out to be a shot rear wheel bearing........even though I could swear I heard it from the front end the axle shaft had a nice groove worn into it when I removed it,I will be replacing the bearing tomorrow

 

All of the above problems solved.....including the clunk when I disengage the 4x4.Just thought that I would share my situation with others as it REALLY felt like a front hub/bearing assembly NOT a rear wheel bearing.