I've had my 2007 AP2 for 27,000 trouble free miles, performed very very regular maintenance with transmission fluid changes every third oil change (change the oil every 1500-2000 miles). All of a sudden, when pulling up to my driveway, near idle I can hear this rattling noise coming from under the vehicle. At first I thought it may of been the heat shield or something, but upon inspection the next day, it seems the source is resonating from the rear of the transmission. This sound is amplified when holding the rev's around 3,000 rpm's in neutral on the driveway, irrespective of the clutch being depressed or not, the noise peaks in that small range of 2,900-3,100 rpms. At an ever-so light application of throttle from idle you can just faintly hear that same noise at a lower pitch. At first I thought it may of been the common clutch buzz, but it occurs whether the clutch is depressed or not, and am now worried I may have damaged a bearing in the transmission, which is a bit disheartening because I've been a heel-toe-r for the past ten years and because of that have never had any issues with any of the transmissions on any of my other vehicles. The noise also occurs when driving and lightly applying throttle to get it around that troublesome rpm of 3,000, and it seems to be more pronounced on deceleration to 3,000 on a revmatched downshift. If someone with some experience could chyme in, it would be greatly appreciated since this car is now my summer treat when I come back home, for I'm abroad for 10 months out of the year, and I so look forward to getting back into this machine which always runs like clockwork.

 

I wonder if it might be an exhaust rattle. Maybe a heatshield around the CAT or maybe an element inside the CAT.

 

It's definitely not exhaust related, tapped all around the exhaust from header down to cat and unable to detect any rattles, everything is still like new without any corrosion, and highly doubt the cat's decayed as it's such low mileage and I haven't had neither a check engine light nor has fuel consumption changed. Almost convinced it's the clutch buzz, but just wanna confirm that my symptoms co-incide with the infamous clutch buzz.

 

I had a rattle under the car. It was the CAT. The mesh inside had slipped and was loose. It also damaged my secondary O2 sensor. You say the noise is also heard with clutch in. If the noise is heard with clutch in and at a stop, I don't see how it could be a transmission problem.

I am no expert on the S. I am just reporting what my issue was. You can hear it at:

[media]http://www.youtube.com/watch?v=qPBqaD3WIb8[/media]