I have a 1992 4x4 (~115,000mi, manual trans) that has developed a notable vibration/sound when driving at all speeds. It almost sounds like there was a tread separation on the tire, but upon inspection everything looks okay. I had the wheels balanced about 400 miles ago. Also, the vibration continues when coasting and goes away under braking. I don't know if its related, but there also seems to be a slight hesitation during acceleration from a stop, but not really when I'm accelerating while already moving,

Does anyone have any ideas on what could be causing this? Could it be a broken axle, u-joint, etc?

Any suggestions would be appreciated.

Thanks