I’ve tried 2 types of rubber bumpers in my 2002 motor and the first one was purchased from NEV Accessories(had a outer diameter gear pattern) lasted only 2 weeks before I got clunking on acceleration/deceleration again. The next one I tried had a smooth outer diameter and it lasted about a month. And these are with the inserted dime trick too.
What also had me curious is why the hollow center in the bumper when the input shaft end is blunt?