Allison Transmission has been a key player in the Military and Heavy Duty Commercial truck markets for many years. These tough vocations require transmissions that are not only capable of heavy loads, rigorous duty cycles, and proven reliability, but also provide value for the end-user and maintain compatibility with leading edge technological improvements of engines and other parts of the vehicle system. The Allison HD4070 transmission is one of the latest transmission offerings from Allison Transmission to meet the “next generation” heavy-duty vehicle needs. This product increases value to the vehicle manufacturer and customer, and provides compatibility with the fast changing electronics capabilities of modern vehicle systems and engines. These improvements are offered in a durable design that has been the trademark of Allison transmissions in these markets. This paper will describe the application, design, development and operational principles of the HD4070 transmission for the military and commercial heavy duty markets.