Yesterday, I noticed for the first time a noise coming from the rear hub. When it first started (fairly abruptly), it sounded just like an out of true rim scrubbing on the brake once per revolution but with a gritty component to the sound. I put the bike on the car rack and found that the noise only happens in freewheel and goes away when there is drive pressure on the hub. The noise is loud enough to sometimes be heard over wind noise at 15-20 mph, especially with a little tail wind and seems to get worse with speed. There is definitely a coarse and gritty feel to the sound though it has to be on the rack to pick that up.
The owner and main mechanic at my LBS will be gone till next Monday and I tend to ride every day. First noticed it yesterday and rode today without noticeable change.
Is this something I need to stay off the bike for until repair?