The John Deere 4055, 4255, and 4455 tractors, produced primarily in the late 1980s and early 1990s, represent robust and reliable heavy-duty utility machines designed for demanding agricultural and construction tasks. These tractors are distinguished by their powerful turbocharged, direct injection diesel engines, advanced hydraulic systems, and comfortable operator stations, offering versatile PTO options and durable drivetrain components. Built upon John Deere's legacy of quality and innovation, these models were engineered for performance and longevity, competing effectively within their segment and earning a reputation for dependable service in challenging environments. This comprehensive manual provides essential information for the repair, operation, and testing of the John Deere 4055, 4255, and 4455 tractors. It covers a wide array of systems, including detailed procedures for engine overhaul, powertrain maintenance, chassis and control system servicing, and hydraulic system repairs. The manual also includes scheduled maintenance guidelines, diagnostic procedures, and safe operational practices, making it an indispensable resource for owners, mechanics, and technicians. With an estimated 1500+ pages of technical information, this combined technical and operation/tests manual is designed to facilitate the efficient maintenance and repair of these tractors.