That's because previous to about 1978 in the middle of QL production, the spherical ball bushing coupler was not in use. Later Quietlines on up used the spherical ball bushing to center the driveshaft. Previous to that, the earlier QLs (and MAYBE the 1x9s) used a steel ball and a large indentation in the back of the driveshaft to center it. Previous to this, all narrowframes (and possibly the 1x9s; I don't know because I've never owned a 1x9) had a 5/16" dia. or so nub on the back of the shaft that very loosely centered in the input shaft coupler with no bushing whatsoever. In that case, the rubber coupling had to keep it somewhat coaxial, but the rear coupler itself kept the driveshaft loosely constrained on the rotating axis of the input shaft. Does that clear anything up?
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