frankie: for starters i would NOT ride it any further until proper diagnosis is done by either you or someone familiar with buell/sportster drivelines. it could be anything from the front rotor attachment nut coming loose to rear input shaft/clutch pack nut coming loose. i would also lift the bike sufficiently so that rear wheel could be spun by hand. do that and see if you have a loud grinding type noise emanating from the front pulley area. if so it is the output shaft main bearing. out of curiousity did you find excessive amount of metal shavings on the primary drain plug when you did fluid change?