I just bought a new 2010 Frontier 4x2 Crew Cab SE. I have only 500 miles on it. There is really annoying low level vibration going on; the passenger seat vibrates, so do the visors, and I can feel every bump on the road. I've taken it to the dealer and they claim they re-adjusted the alignment but it seems the same. It really annoying to see with your peripheral vision the seat shaking. Any Suggestions?