three weeks ago I replaced the struts, ball joints, tie rods, put in some ford racing lowering springs, new sway bar, end links and bushings. After which I got it aligned and new pony mags with some Kelly springfield tires. Not consistently, but every 4th or 5th time I take it for a drive, when I go over rivets in the ground or bumps, I get a knocking and a loud crack underneath my car. I've taken it to my shop and looked, also took it to two shops apart from my own. Anyone experienced this problem or something similar? Its hitting the floor pan so :S.