We have exactly the same setup in our class room, it works wonderfully to explain it Sent from my iPhone using H.A.M.B.
Oscillating, almost Constant Velocity. Make the trans output, and the pinion input angles Equal and opposite, at loaded 'ride' height. That way you cancel the occilation. Is said, joint angles of 3 degrees is sufficient to move lube in the joints. "Hey Ned, confirm? Adjust?"