2000 4.6 136K with a vibration under load/acceleratoin. When starting from stop and slowly progress through shifts it feels smooth as can be. Soon as I accerelerate, even moderately get on it, I start to get a vibration. Wheel Alignment Center said it is absolutley not alignment or wheel balance related. So then it has to be Drive Shaft Imbalnace, Original U-Joints, Harmonic Balance, Half Shafts or Transmission? Anyone with similar problem, please let me know what your solution was?