In the early 1960s, Mack Truck's executive vice president of product and engineering, Walter May, developed the Maxidyne high-torque rise engine. The engine was introduced as an inline six in 1966, as a V8 in 1970, and as the intercooled inline six 300 series in 1973. This was an industry-changing event. The Maxidyne, with an operating range of 1200–2100 R.P.M, and later 1050–1700 R.P.M., allowed a heavy Class 8 truck to be operated with a 5 speed (Maxitorque) transmission. Previously, heavy trucks typically operated between 1800-2100R.P.M. and were equipped with 10 or more gears.