ST1100Y
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Well, (significant) wear of the "bearing boss" on the wheel allows the splines to be driven out its counterpart in the ring-gear (forcing it closer to the wheel), thus only the outer 5mm "tips" of the splines where mashing/transferring torque...Have pulled wheel and drive flange splines are almost gone but only on the ends bout 5mm. Drive hub splines also look worn (I take it these are supposed to look squared when in good condition. mine are like wedges)
You will need a new rear wheel (+ bearings and seal), cush-rubbers + aluminium inserts, new drive splines, at least the two O-rings (one on the "bearing boss", the next on the splines) and a good dip of Moly lube.
I'd also inspect the inside of the ring-gear for significant wear, cause if present, it'll will grind down your new splines rather quickly...