We were making some beeritas (half frozen margarita, half beer, discovered on a trip to Chicago of all places) yesterday. Our old Kitchenaid (model KSB5WH) blender stripped out the rubber coupling on the motor. Bummer. This was an expensive blender back when we bought it, before there was enough internet that you could read 100 reviews before any purchase.
A little googling and voila..the coupler is a 9701057 and can be ordered from these guys. There’s even directions for removing the old coupling (Hint: It’s reverse threaded, so think righty-loosey.)