I am leasing a pre owned volvo certified S70. Sometime while I am driving very slow and step on the gas suddenly I hear like a clunking noise. Sometimes when I am coming to stop and the tranmission is down shifting, I also feel the clunking or a sensation that something is loose (or knocking) in the front drivetrain. A friend and me have checked underneath the car and everything appear to be secured. We even changed the top engine torque bushing point which was cracked. Very easy and inexpensive by the way! Any other suggestion, it is not a major problem, but I do not want it to become one if I can help it!