2002 Honda Civic EX. The car rides smoothly and just fine except for when I go over any significant bump faster than 10 mph. If I go over a bump slowly everything in the front end seems to respond as it should but when I hit a pothole or go over a transition such as a steep driveway quickly, I hear a "clunk" coming from the front end. Any ideas what it is and how much it would cost to fix?