This manual covers the Valtra Valmet 8400 and 8400E tractor models, renowned for their robust engineering and reliability in demanding agricultural and industrial applications. Valtra, with a long heritage of producing durable machinery, designed these tractors to offer significant power and advanced features for their era. The 8400 series represents a notable advancement in Valtra's tractor development, built to provide efficient performance and value. This comprehensive workshop service and repair manual is an essential resource for understanding and maintaining these powerful machines. The purpose of this 1361-page English-language workshop service repair manual is to provide detailed guidance for the maintenance, troubleshooting, and repair of the Valtra Valmet 8400/8400E tractors. It covers all major systems, including engine, transmission, hydraulics, electrical, braking, and steering. The manual includes step-by-step instructions for routine maintenance, component overhaul, disassembly and assembly, and the use of special tools. Safety is emphasized throughout, with clear notations for warnings and precautions. This resource is designed for mechanical technicians and knowledgeable owners, enabling them to perform high-quality work and ensure the longevity and optimal performance of their tractor.