This manual covers the Allison Transmission 4000 MH, equipped with 4th Generation Controls. Designed for robust performance and reliability, this transmission is engineered for demanding applications. It offers optional Power Takeoff (PTO) and output retarder features to enhance its versatility. The 4000 MH is built with a focus on engineering quality, ensuring dependable operation across a wide range of uses. This comprehensive service repair manual provides detailed procedures for the overhaul, disassembly, rebuild, and reassembly of the Allison Transmission 4000 MH. It includes essential information such as part inspection, wear limits, spring data, and customer service details. The manual is structured to guide owners, mechanics, and technicians through maintenance and repair tasks, offering step-by-step instructions and detailed illustrations to facilitate accurate work and potentially reduce repair expenses.