I'm not sure how many miles are on my cassette but I don't think it's more than 5,000 and maybe less (can't remember if I moved it from another wheel or installed a new one). The chain, however was getting ready to replace. Stretch was between 1/16 and 1/8. First ride on the new chain I noticed an odd, clicking or pulsating sound on each downstroke under hard pedaling like when climbing. Hard to describe, but it's a kind of dull tick, tick, tick...tick, tick, tick. My only thought was maybe the cassette is worn but seems much too soon for that.
Any thoughts? Thanks.