Craftsman Ryobi Tiller Gear Case Shaft Spur Gear 717-1585 Genuine OEM Replacement Fits Craftsman MTD Ryobi. This is a Genuine OEM Craftsman part. This gear case shaft spur gear (part number 717-1585) is for tillers. Gear case shaft spur gear 717-1585 drives the input sprockets inside the gear case. Wear work gloves to protect your hands when installing thi... - Craftsman Ryobi Tiller Gear Case Shaft Spur Gear 717-1585 Genuine OEM Replacement Fits Craftsman MTD Ryobi.