Ok so here's my situation. My 96 trek 1000 road bike makes rattling/clicking noise whenever I pedal front or backwards. I take it to the LBS and they say I need new chain, middle chain ring, and cassette. I went home and replaced all three of those, but it still makes a noise. The noise is less loud now but it's still there. I have located the noise to the rear derailleur. Sounds like whenever a link comes into contact with the pulleys it makes a slight sound. My rear derailleur is shimano sora 9spd. The cassette is 8 speed and so is the chain. Could it be that the 9 speed does not work with 8 speed? Please let me know what you think.