I would not go copper i would go ceramic the only thing i can think of that would cause this problem is either your gear mesh is to tight or the shaft in your motor is off and i do not think it is either one because i know you can set up your car right and i do not think O.S. would send out a product like that.

try getting a new bell clutch maby that has a problem. i have no idea other than that.

What bearings are you buying now?