Ive owned my 2004 SLK 230, auto 2.3 litre 170 model almost a week now and just getting used to the quirks. One quirk particularly bothers me is on revving up and down there is at about 1200-1300 revs a distinct sound like a very rattly bearing. The sound lasts only about half a second and seems only at those revs and is independent of speed or gear. The car has 91,000 miles. particularly noticeable roof down at gentle speeds as l go on and off throttle. Any and all advice appreciated.