Probably not the same issue, but a few month's ago my wife's 05 300C started rattling a little over some bumps. I got it up on the rack and discovered the brace that runs under the exhaust was only clearing the pipes by about 1/16", so I dropped it and slid a washer under each bolt. No rattle anymore. Of course, last year I had to replace both outer tie rod ends at 70k, so I agree with what was said earlier about the front ends being junk on these cars!