When I was driving home yesterday i noticed a vibration through my floorboard that shouldn't be there. It wasn't really consistent. The farther I drove, it started to make a growling which I thought was from the wheel bearing but didn't stop when I was sitting at a light. If i hit the throttle the growl went away, also didn't make a difference if the clutch was in or out, in gear or out of gear and when I put it in gear and take off it goes away. The clutch doesn't slip, I haven't smelled it burning and the trans shifts perfectly. the only thing I can think of is that the dual mass flywheel is messed up or a motor mount. The truck has 120,000 miles on it with what I assume is the original clutch. Any help would be greatly appreciated, I don't feel like putting in a new clutch if I don't have to.