Yamaha - Gear - 69K-45571-00-00Yamaha Gear Lower Unit Drivetrain Component 69K 45571 00 00 Overview Down in the lower unit, gears are constantly under load, especially when youre shifting or pushing the motor hard. When everythings in good shape, its smooth and quiet, and you dont think about it. But once a gear starts wearing out, youll hear the noise or feel the vibration pretty quick. Replacing a worn gear like this keeps the drivetrain tight and prevents bigger issues from