release lever 分离杆 gear ratio 传动比 reduction gear减速档 direct drive gear直接档 overdrive gear超速档 differentia|gear差速器 reverse gear 倒档 fuel mileage 燃油经济性 shifting 换档机构 mechanism extension 加长壳,后壳 housing precision 精密机械 machineryrelease lever 分离杆 gear ratio 传动比 reduction gear 减速档 direct drive gear 直接档 overdrive gear 超速档 differential gear 差速器 reverse gear 倒档 fuel mileage 燃油经济性 shifting mechanism 换档机构 extension housing 加长壳，后壳 precision machinery 精密机械