Started hearing a noise at low speed. squeak groan intermediate, loud enough to hear through helmet. Pulled rear end oil good no metal parts on magnet, no side play in bearings, gear backlash seems good. no problems with drive shaft, I'm not really hard on bike at all. Did replace both rear swing arm bearings they were a little rough. reassembled thinking maybe bearing noise from swing arm being amplified through hollow swing arm. Noise still there. Noise quits when pulling in clutch and coasting. seems really loud when engine not really pulling but when engine between power on and power off, drained transmission oil no metal parts but the usual metal silver sludge. I'm thinking maybe it is the coupling on the input shaft that is spring loaded that takes up engine surges in transmission. Clutch wear normal nothing loose. Waiting on tool to pull transmission cases apart. I'm a very competent mechanic work for Catarpillar as field tech. Noise has me baffled because it is not normal noise. And it has just started. There does seem to be a lot of backlash in rear wheel. but it is not in rear end gear assembly. I know transmission gears have engagement dogs between gears but this seems extreme that is why I'm thinking it is the coupling in transmission. Would really appreciate any comments. really want to keep the bike it has been mine since new and I don't really want to upgrade. Thanks