I still cannot find a solution to this problem. I had the car state inspected today and it passed with flying colors. I can still hear that knocking-thumping sound. The steering shaft feels and looks tight. The struts look good, they are tight, and there is no oil leaks visible. I verified that the sway bar bushing were the correct ones with the dealership. Could this be the rack and pinion? When I turn the wheel, without the motor running, back and forth quickly, there is a clicking noise. There is no clicking noise when the motor is running. Thoughts anyone?