Yamaha - GEAR, DRIVEN - 6AH-11537-00-00Yamaha Driven Gear Internal Engine Gear System 6AH 11537 00 00 Overview Inside the engine, this driven gear is part of what keeps everything turning in sync. When its in good shape, the motor runs smooth and quiet without any extra noise or vibration. But once wear starts or teeth get damaged, youll hear itand it usually doesnt take long to get worse. Its one of those internal parts that has to be right if you want the engine to keep running strong.