Well, when it rains it pours for me it seems. The ring slipped off of the harmonic balancer and is spinning around between the hub it was on and the main pulley. It sounded exactly like the fan was hitting something and it only makes sound when it's idling or coming down from higher RPM. It may have slipped off halfway into my 40 mile commute for all I know since it makes zero noise when you're going down the road. I'm not very familiar with externally balanced engines. Is the counterweight in the hub like I'm assuming? Is it safe to drive home?