I just bought a used 70-200 f4L (non-IS). Got it from a dealer, date code Y, looks brand new. Everything seems to work fine - focus is normally fast, seems accurate, but it's a bit noisy. There's a bit of a "rattle" or "clatter" as it focuses (but the manual focus ring turns very smoothly). It's not a loud noise, but clearly audible a few feet away. I owned one of these awhile back and seem to remember it was very quiet - just a soft swish as it focused. Anyone know if this sound is common for this lens? I don't want to send a good lens back if this is nothing to worry about.