This manual covers the Allison 4000 HS automatic transmission, featuring 4th Generation Controls. Designed for robust performance and reliability, this transmission is engineered for demanding applications. It incorporates advanced control systems to optimize operation and efficiency. The Allison 4000 HS is built with quality and durability in mind, ensuring consistent performance across various operational conditions. This Service Repair Manual provides comprehensive guidance for maintaining and repairing the Allison 4000 HS transmission. It includes detailed procedures for disassembly, rebuild, and reassembly, along with part inspection instructions and wear limit data. The manual also covers the principles of operation for the 3000 and 4000 Product Families, and details optional features such as Power Takeoff (PTO) and output retarders. With clear line drawings, cross-sectional views, and hydraulic schematics, this manual is an essential resource for owners, mechanics, and technicians.