Yamaha Gear Case Metal YA2-10705-47-08. Overview. The Yamaha Gear Case Metal YA2-10705-47-08 is a genuine original equipment manufacturer component designed to provide structural support and protection within the gear case assembly. This part plays an important role in maintaining the integrity of the gear housing, helping to protect internal components from wear, contamination, and external damage.. A properly maintained gear case is essential for smooth power transfer and reliable engine opera