The Hitachi ZX40U-3 and ZX50U-3 compact excavators represent a significant advancement in their class, built upon the robust "Dash 3" generation engineering. These machines are designed for efficiency and reliability in a wide range of construction and landscaping applications. Their compact size, combined with powerful diesel engines and advanced hydrostatic transmissions, allows for precise operation in confined spaces while delivering the performance expected from larger equipment. The inclusion of standard features such as joystick and pilot controls further enhances operator comfort and productivity, making them a valuable asset for any project. This full service repair manual provides comprehensive guidance for the maintenance and repair of the Hitachi ZX40U-3 and ZX50U-3 excavators. It covers essential areas including detailed maintenance procedures, troubleshooting diagnostics, technical specifications, and critical safety guidelines. By offering in-depth information on the hydraulic system, undercarriage, and engine components, this manual serves as an indispensable resource for owners, mechanics, and technicians. Its purpose is to ensure the longevity, optimal performance, and safe operation of these sophisticated machines through accurate and thorough documentation.