Well, the noise is hard to describe. I was able to reproduce it again today and went to the back of the car to listen a little better.

It sounded more like a faint scraping, like there was something rotating and lightly grinding against something. From a distance, its faint enough to sound like a whirring or fan, but it isn't.

I've got an early AM appt with HBL in VA tomorrow, so I'm gonna have them check it out.