This manual covers the Allison 3000 and 4000 Series Gearbox Workshop Service Manual. These transmissions are engineered for robust performance and reliability across a wide range of applications. The 4000 Series transmissions feature WTEC II and WTEC III control systems, ensuring efficient operation. This comprehensive guide is designed to support the correct service, maintenance, and repair of these high-quality gearboxes. The purpose of this workshop service manual is to provide detailed instructions and specifications for maintaining and repairing the Allison 3000 and 4000 Series transmissions. It includes extensive information on general procedures, diagnosis, preventive maintenance, overhaul, and assembly, supported by pictures and diagrams. This manual is fully printable and aims to assist owners, mechanics, and technicians in ensuring the optimal performance and longevity of their Allison transmissions.