When I accelerate anywhere under 40 mph, I can feel a vibration channel through the driveshaft. It starts from the front, then works it's way back. If you put your hand around the center bump in front of the middle of the backseat of the 350, you can feel the vibration. However, at 50 mph the car is smooth. Have talked to many owners and they have never run into this before.

Perhaps you guys can help me.