Yamaha Gear Case Assembly YA2-10705-45-08. Overview. The Yamaha Gear Case Assembly YA2-10705-45-08 is a genuine original equipment manufacturer component designed to house and protect the internal gearing responsible for transferring engine power efficiently. This assembly plays a vital role in ensuring smooth operation, proper alignment, and reliable power delivery throughout the drivetrain.. A well-functioning gear case assembly is essential for maintaining performance and preventing internal