Yamaha - Gear 1 Assembly Drivetrain Component 6K1-45560-01-00. Overview. The Yamaha Gear 1 Assembly 6K1-45560-01-00 is one of those parts deep in the lower unit that you don't notice-until something goes wrong. When gears start wearing out, you'll hear it first, then feel it when the boat's under load. This assembly plays a key role in transferring power smoothly, so everything stays tight and predictable when you shift and throttle up. If you're already inside the gearcase, replacing it now saves you from bigger problems later.. Key Features. • Integrated Gear Assembly - Combines matched components for smooth and consistent drivetrain operation.. • Efficient Power Transfer - Helps move engine output cleanly through the lower unit.. • Precision Alignment Design - Built to fit correctly within Yamaha gearcase tolerances.. • High-Load Strength - Handles torque and stress from regular use on the water.. Compatibility. Compatible with select Yamaha outboard engines using this Gear 1 assemb