Ive developed a clicking in my rear derailleur - it only happens on certain gears, particularly the 2nd-4th smallest. The vibration from the clicking translates all the way up to pedals and is ridiculously distracting. I cant pinpoint it beyond coming from my derailleur, possibly the cage. The derailleur is otherwise in perfect shape, relatively new and shifts fine. Im having issues with my LBS, and would rather fix it myself or just buy a part rather than ask them for help. Any suggestions as to what the mystery click/vibration might be?
Possibly a stiff, sticky, or slightly bent chain link? Is your chain new?