Steve, I Hear Ya', But........
What ever is causing it is so serious of an amount of play that it interferes with the cruise control. With the control on, and the car on a down hill slope, there is so much play that the car jerks, or rocks, back and forth against the two points of play. That just doesn't seem normal to me.
And I've changed out both of the rubber rings on the ends of the drive shaft. One was admittedly bad, but not the other. And the car still does this.