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In the 1950s, Caterpillar adopted several improvements to its tractors: the wet clutch (improving clutch life), turbochargers (increasing power), and the "powershift" transmission (eliminating the flywheel clutch lever, the gearshift lever, and the forward and reverse levers).
In 1954, Caterpillar introduced its largest tractor to date, the D9D. Entering production in 1955, it was offered in two models - the direct-drive transmission and the torque converter drive. In 1959 the new D9E was introduced, being a more powerful tractor, in three versions - the direct drive, the torque converter drive, and with powershift. In 1961, the D9E was replaced with the D9G, with powershift transmission standard.
In the mid-1960s, in order to meet the needs of the large farms and ranches of the West, especially in the wheat-raising areas, Caterpillar engineered tractors, styling them the "Special Application" tractors - D4, D5, and D6. The "SA" models, engineered for drawbar work (i.e., pulling agricultural implements), offered direct-drive transmissions, variable horsepower in higher gears, full-length fenders to reduce dust reaching the operator from the fast-moving tracks, and more creature comforts.
Here ends our brief history of Caterpillar. The Antique Caterpillar Machinery Owners Club is interested in Caterpillar equipment that is 40 years old, or older. The early to mid-1960s represents the newest equipment of which we take official notice. We hope that you have found this brief history instructive. If you are interested, we have also placed a history of our club on the homepage of our website. Thank you for looking!
For further information, here is a list of books that are currently in print. We encourage you to read them for a fuller appreciation of the history of Caterpillar equipment and the companies involved in manufacturing them.
Caterpillar, by Randy Leffingwell (Osceola, WI: Motorbooks International, 1994), ISBN 0-87938-921-4
Caterpillar Century, by Eric C. Orlemann (St. Paul, MN: Motorbooks International, 2003), ISBN 0-7603-1604-X
Caterpillar's Roots, by Jack Alexander
Additionally, portions of this site may have been reviewed by Caterpillar Inc. Corporate Archives.