Automatic Transmissions in America

Abstract

Since the internal-combustion engine was first adopted for automotive use, American industry has conducted a constant search for a transmission with infinitely variable ratio, fully automatic operation, and high efficiency. The fully automatic transmission has now evolved into a unit providing greater safety and ease of operation for the driver. It is no longer considered novelty or luxury equipment in the passenger car and its value is rapidly becoming recognized in commercial applications. Engineering research and development in the United States of America has been active in this search for two decades. The first approach was the development of friction, electrical, and hydraulic displacement drives, all of which resulted in bulky and heavy mechanisms inefficient and impractical in use. Then came the development of hydrodynamic drives, the fluid coupling, and the torque converter. Here, continual commercial successes have been made. The first use of the torque converter was in city service 'buses in 1934, replacing the manual shift transmission which was subjected to a gear shift every eleven seconds of its operation. In 1939, the first successful automatic passenger-car transmission, the Hydra-Matic, was produced. From that date onwards all competitive American passenger-car manufacturers followed in suit with their own designs. In many cases, the different transmissions have been mere re-arrangements of already proven designs, the features chosen representing the respective engineer-management judgement of the desirability of the various characteristics of known automatic transmissions. The extent of the field is evidence by the production of automatic transmissions in the United States of America, which in 1951 was 2,422,131 units. While development work was progressing in the passenger car field, the field which offers the greatest promise of commercial rewards, extensive activity was also prevailing in the commercial and military fields. Here engineering research and development has led to the design and current production of automatic drives, using either the fluid coupling or torque converter, for use in highway and off-highway trucks, earth-moving equipment, cranes and hoists, railroad equipment, oil-well servicing and drilling equipment, and, in the logging industry, yarders and hauling equipment. Military applications are currently being made in all weights of tanks, trucks, and track-laying vehicles. So it can be seen that the scope of the American field of automatic transmissions is large and the development has been extensive. It has an interesting history and the field shows promise of still further gains.