The Hitachi ZAXIS 40U and 50U are robust excavators designed for demanding work environments. These machines feature a powerful diesel engine and a water-cooled system, ensuring efficient operation. Their hydrostatic transmission with variable speed hydraulic control offers precise maneuverability. The ZAXIS 40U has an operating weight of approximately 3,800 kg and transport dimensions of 5,100 mm length, 1,700 mm width, and 2,450 mm height. The larger ZAXIS 50U weighs approximately 4,900 kg and has transport dimensions of 5,400 mm length, 1,850 mm width, and 2,550 mm height. These excavators are engineered for reliability and performance in various construction and excavation applications. This service manual provides comprehensive information for the Hitachi ZAXIS 40U and 50U excavators. It covers essential maintenance procedures, including recommended intervals for engine oil changes, hydraulic filter replacement, and air filter cleaning, directing users to consult the manual for specific details. The manual also details technical specifications and operational guidelines. Its purpose is to assist owners, mechanics, and technicians in performing routine maintenance, troubleshooting issues, and ensuring the optimal performance and longevity of these diesel-powered, water-cooled excavators.