Yamaha - Gear - 69L-45571-00-00Yamaha Gear Lower Unit Drivetrain Component 69L 45571 00 00 Overview Inside the lower unit, gears are constantly working under load, especially when youre shifting or running at speed. When everythings in good shape, its quiet, smooth, and you dont think twice about it. But once a gear starts wearing down, youll feel it with vibration or hear it right away. Its one of those parts you replace to keep the drivetrain tight and avoid bigger issues down