The New Holland T9 Series, encompassing models T9.390 through T9.670, represents a line of high-horsepower articulated four-wheel-drive agricultural tractors engineered for demanding field operations. These tractors are built upon a legacy of robust design, offering exceptional power and reliability for farmers and agricultural contractors. Featuring advanced engine technology, typically from Cummins, with power outputs ranging from approximately 390 to 670 horsepower, and equipped with sophisticated transmission options such as powershift or Continuously Variable Transmission (CVT), the T9 Series is designed for optimal performance and efficiency in heavy draft applications. Their articulated steering ensures superior maneuverability, while the operator station is designed for comfort and safety, often including ROPS and FOPS compliant cabs. This comprehensive Factory Service Repair Manual provides detailed technical information and procedures for the New Holland T9 Series tractors. It covers all major systems, including engine service and overhaul, powertrain components like transmissions and differentials, hydraulic systems, electrical and electronic controls, chassis, frame, and the operator station. The manual includes essential maintenance schedules, lubrication guidelines, troubleshooting diagnostics, repair instructions, and disassembly/reassembly procedures, all supported by high-quality diagrams and illustrations. With factory-level detail and diagnostic charts, this manual is an indispensable resource for owners, mechanics, and technicians to ensure the continued optimal performance, reliability, and longevity of their T9 Series tractors.