It sure is good to find the source of such a noise. I had a somewhat similar thing. The lower shock bolt, although tight, was not gripping the inner shock bushing tight enough to keep it from using the clearance around the bolt to move and make a knocking sound that could be felt. I had to over torque the bolts to make the noise quit. And i DO MEAN OVER TORQUE. I stopped tightening just before she broke :--)