Have any of you experienced this? I drive an 00 V8 Sport. A month ago I started hearing this rattle under the car (towards the driver side rear). At start-up, car sounds fine. After idle drops to 800rpm, I hear this rattle. It'll last for about 3-5 seconds. Don't know if it's the differential, cats, or muffler. No CEL has come up. Car seems to run fine, no hesitation, no sulfur odor either. It rattles when I'm changing from Park to Reverse and/or Reverse to D5 (from cold start). Switched over to SST, to check if it's a tranny issue, but car runs fine. Any ideas? Thanx in advance.