Ya true I was just looking at the rear coils and thinking the same thing. I had the strut mount replaced and the control arm bushing to get rid of what I think patrickd_21 is mentioning. Both had some play in my situation. I could reproduce the sound by hitting small speed bumps faster than normal, or by going up a driveway with that tiny concrete raiser on it fast. Drove me nuts too.. and unless one can do the strut mounts oneself, it might be worth upgrading while fixing.