On my ride yesterday I noticed a light click coming from my drive train. It seemed to be more in time with the cassette rotation so I suspected the rear wheel. When I got home I swapped rear wheels and the noise went away.
The rear wheel in question is a Mavic Open Pro laced to a 105 10-speed hub, 3-cross. The wheel/hub probably has 3 - 4 thousand miles. The cassette, probably fewer but still a couple thousand. The chain is relatively new.
First I checked all the spokes and they seemed fine. I took the cassette, axle and freehub off, cleaned them, re-lubed and re-installed them. This was the first time I had removed a free hub and did not dis-assemble it...I threw some new grease on the inside bearings and put it back.
After getting everything back together, I took if for a ride and the sound is still there. It only makes the sound when I'm on the bike...not on the stand. It clicks more with cassette rotation and will actually click one or two more times after I stop pedaling.
So...here's my next two best guesses. Freehub is indeed going out...I just didn't do enough to it to make the sound go away. or my cassette is worn and needs replacing, although the sound seemed to be present across a range of sprockets.
Anything else I might be missing?