help indexing gears

fattywilliams

hi there my wet weather bike (GT gts sport) with 8pd claris on has annoying clicking type noise from rear mech now it pretty much done this out the box as far as i can recall Ive tried adjusting the indexing on the rear mech which seems not to really effect it. intrestingly though its only when its in the big ring it is silky and smooth in the little ring but the noice is defiently not coming from front mech so i cant really work out how to fix this any thoughts?