This workshop service manual covers the Hyundai HDF 20-5, HDF 25-5, and HDF 30-5 forklift trucks. These models, manufactured by Hyundai Heavy Industries, are known for their robust engineering and reliability in industrial applications. The HDF series represents a generation of forklifts designed for improved performance, with lifting capacities ranging from 2.0 to 3.0 tonnes. They are powered by the efficient Yanmar 4TNE98-HYF 3.3L inline 4-cylinder diesel engine, featuring overhead camshaft technology. This manual is specifically tailored to these models, providing in-depth information to ensure optimal operation and longevity. This comprehensive manual serves as an essential resource for owners, mechanics, and technicians, offering detailed guidance on maintenance, repair, and troubleshooting. It covers all major systems, including the engine, powertrain, hydraulic system with its intricate control valve and gear pump, electrical system with detailed wiring diagrams, and brake and steering systems. Procedures for disassembly, assembly, and installation of components, along with specific tightening torque values and special tool requirements, are thoroughly explained. The manual also includes periodic maintenance schedules, lubrication charts, and diagnostic information, all presented with clear illustrations and step-by-step instructions to facilitate efficient and accurate service.