I just purchased a pre-owned 2000 M5 with 26,000 kms. I recently noticed that when I shut off the engine, I hear a grrrrrr type of noise. Sounds like vibrating gears. I took it to the dealer today and they told me that the noise is normal. They say some M5s are louder than others but it's normal. The tech had me press the clutch while turning the engine off and the noise was gone. He said the noise is from rattling of the plates or something like that. Can any one shed some light on this? The only way to turn off the car without this annoying sound is to engage the clutch. Pls advise.