Developments in truck automatic transmissions

Automatic transmissions have been available for application to buses, heavy duty trucks and off highway vehicles for a number of years. Until recently, most of these transmissions have utilized hydraulic controls similar to the type used on automatic automobile transmissions. Availability of low cost, microcomputer based electronics offers the opportunity to replace these hydraulic controls with electrohydraulic controls resulting in improved fuel economy, enhanced performance, unexcelled vocational adaptability, increased customer satisfaction, and a number of manufacturing benefits. Electronic transmission controls are not new. In the late 1960's, detroit diesel allison (dda) division of general motors corporation introduced automatic discrete component, open loop electronic transmission controls for heavy duty off highway vehicles such as earth movers, large deep pit mining trucks, and oil field rigs. These controls effectively reduced vehicle operating costs and increased vehicle availability. Since 1978, dda has been developing new microcomputer based electronic controls to provide a cost effective system for the smaller on highway transmission applications. Although this new system is being developed for initial introduction to the on highway market, it will subsequently be utilized in the off highway market resulting in reduced system costs for the larger off highway vehicles. The new microcomputer based system has been named the allison electronic transmission controls (atec) system.