Yamaha - Gear 2 Lower Unit Drivetrain Component 6J9-45571-02-00. Overview. When gears start wearing down, you'll usually hear it first-noise, rough engagement, or that uneasy feeling when shifting. This gear plays a key role in how power gets transferred through the lower unit, so it needs to be solid. I've worked on units where replacing a worn gear made everything feel tighter and quieter right away. It's one of those internal parts that keeps the whole drivetrain working the way it should.. Key Features. Precision Gear Engagement - Designed for smooth interaction with mating gears inside the lower unit.. High-Strength Construction - Built to handle constant load and rotational stress.. Reduced Mechanical Noise - Helps maintain quiet and efficient operation when properly installed.. Factory-Spec Fitment - Ensures correct alignment within Yamaha drivetrain assemblies.. Wear-Resistant Design - Engineered for long-term durability under marine conditions.. Engine & Boat Compatibility. De