Peter-

Is there actually slop between the adapter and the splined input shaft of the rack, or is it the other end of the input shaft where it interfaces with the rack?

I would suspect it is the later. The splines themselves should not wear (unless they were loose). I would suspect you have worn out the rack by causing it to turn those 35's (+/- the locker).

Time to find a jy rack.

Good Luck,
Michael