That's a very interesting thought.. I'm going to a smaller pulley (does away with the clutch assembly) in about a month. I'll keep this thread updated if that has any effect.It almost sounds to me like metal on metal spinning. I think I recall seeing the new cars have a clutch on the supercharger pulley. I wonder if your clutch engagement is out of square, so it slips on part of the disc before it fully engages?