This manual covers the Allison 3000 & 4000 Series automatic gearboxes, designed for robust performance and reliability. These transmissions are engineered to integrate seamlessly with a variety of diesel engines, offering efficient power delivery for demanding applications. Their advanced design ensures durability and optimal functionality, making them a preferred choice for commercial and heavy-duty vehicles. The series features multiple forward gears and reverse, providing versatile operational capabilities. This comprehensive service repair manual provides detailed information essential for the maintenance and repair of the Allison 3000 & 4000 Series gearboxes. It includes step-by-step instructions, detailed illustrations, electrical diagrams, and troubleshooting guidance. The manual covers a wide range of systems, including the transmission itself, driveline, and associated components. Owners, technicians, and mechanics will find the critical information, including fluid specifications and capacities, necessary to ensure the longevity and optimal performance of their Allison transmissions.