This comprehensive service manual covers the Hyundai HDF 20-5, HDF 25-5, and HDF 30-5 forklift trucks. These models are engineered for robust performance and reliability in demanding industrial environments, featuring the efficient 3.3L 4-cylinder Yanmar 4TNE98-HYF diesel engine. This manual provides detailed information essential for understanding, maintaining, and repairing these powerful machines, ensuring their continued operational excellence. The purpose of this manual is to serve as a complete guide for all service and repair operations. It includes detailed sections on general information, specifications, periodic maintenance, troubleshooting procedures, and in-depth coverage of all major systems such as the powertrain, hydraulic, steering, and electrical systems. With step-by-step instructions, detailed illustrations, and diagrams, this manual empowers owners, mechanics, and technicians to perform maintenance and repairs accurately and efficiently.