The Komatsu SK815-5n and SK815-5na are robust skid steer loaders designed for demanding operational environments. These machines are engineered with a focus on reliability and performance, featuring powerful diesel engines, including the 4D88E-5 and 4D84E-5 models, and a hydrostatic transmission (HST) for efficient power delivery. Their construction emphasizes durability, making them suitable for a wide range of construction, agricultural, and landscaping tasks. The SK815-5n and SK815-5na represent Komatsu's commitment to providing high-quality, dependable equipment for professional use. This Service Repair Manual provides comprehensive guidance for the maintenance, repair, and troubleshooting of the Komatsu SK815-5n and SK815-5na skid steer loaders. It covers essential areas such as engine components, hydrostatic transmission systems, and a vast array of structural and mechanical parts. Detailed procedures, diagnostic information, standard value tables, and disassembly/assembly instructions are included, supported by detailed illustrations and diagrams. This manual is an indispensable resource for owners, technicians, and mechanics seeking to ensure the optimal performance and longevity of their equipment.