I'd loosen up the rear axle and the 4 bolts that hold the drive unit to the swingarm. Retorque the axle and then tighten the 4 bolts. The wheel flange splines are worn a bit, as you stated. This may be the source of noise.
had thought of that think will start there. Is that something need to get the weight off of the wheel for or is just loosening and retorqueing everything in the right order ok to do with the bike on the ground?