Thanks for your responses guys. The noise can possibly be coming from the bevel box and it may in fact be the swing arm, but I never had this noise until yesterday and it started soon after that initial clanking when I "banged" it into 2nd gear under full acceleration. It was during that shift that I heard the same noise....it was quite a bit louder though and it almost sounded like something snapped. I was also under full throttle, so the belt drive must have been at full tension. I also currently hear the sounds while accelerating.
It sounds like something came loose, but I jacked the car up and checked below and i didn't notice anything out of sorts.
I know the M3W is quirky and generates a ton of strange sounds, but this is one that is beginning to worry me.
