I own a '04 MC with 60k+ miles and have started hearing a loud hum while in gear. Gets loudest at 3k RPM and disappears when the clutch is engaged and the MC is taken out of gear. There is no clicking sounds, or rolling marble sounds like I have read in other posts. My mechanic pulled the drain plugs, saw a lot of shavings on the magnet and said the transmission needs to be replaced. But I have read and seen photos of this and no one seems to thinks twice about it.

Any thoughts?