Front End Vibration - 99 Sierra Z71

[Ganudorm]

I woke up one morning hopped in my truck and was headed to campus going down a hill when I hit 45mph and noticed a vibration in my front end. As I began to diagnose the problem more I noticed it seemed to only be coming from my front driver's side tire. I drove home from college and it was a miserable ride. Whenever I hit about 45mph the front end would start vibrating progressively worse up until about 80mph. At 80mph the roughness seem to "smooth out" but still wasn't normal. I noticed when I went up hills and the engine had to do a little extra work it felt like my engine was going to jump out from under my hood and made the vibrating even worse. I got home and had my rear brakes done because my pads were low and squeaking and got the mechanic to rotate that front driver's side tire to the back to see if the tire was just off balance. Moving the tire didn't help anything, and although I believe that tire was off-balance, the vibration is still there and makes my truck hard to drive over 45. The problem was random and I'm contemplating how to diagnose and fix the problem. The truck is a 1999 GMC Sierra Z71.

[Ganudorm]

any ideas?

[Nice rig]

Jack up the front end, grab front tire at the top and try to move it in and out...if it moves, your hub is going out. Hope this helps narrrow it down.