The Hitachi ZX40U-3 and ZX50U-3 compact excavators, part of the U-3 Series, are engineered for robust performance and reliability in demanding construction and landscaping applications. These machines feature efficient diesel engines, hydrostatic transmissions for precise control, and durable undercarriages with rubber tracks, offering versatility across various job sites. Their design prioritizes operator comfort and productivity, making them valuable assets for professionals requiring powerful and maneuverable equipment. This Service and Repair Manual provides comprehensive guidance for the maintenance and repair of the Hitachi ZX40U-3 and ZX50U-3 excavators. It covers essential information including detailed technical specifications, routine maintenance schedules, lubrication requirements, and procedures for filter replacement. The manual is an indispensable resource for owners, technicians, and mechanics, enabling them to ensure the optimal performance, longevity, and safe operation of their equipment through accurate troubleshooting and repair guidance.