I put new bearings and oil in when I did my engine rebuild but it is not a service item. There is an allen head plug on the back of the supercharger with the gears in it. It would be very difficult to empty it while it is on the car so I would just leave it alone. The way I emptied it was taking the entire unit apart. The rocks noise you heard originally was not coming from the gears in the back, it was coming from the known issue with the isolator in the front. AFAIK nobody has had failures from the gear box.