A Caterpillar D4 is a model of bulldozer, or crawler tractor, manufactured by the Caterpillar company between 1938 and 1957. Caterpillar produced the tractor in its Peoria, Illinois, factory. The D4 used a liquid-cooled four-cylinder diesel engine that produced around 60 horsepower and 421 foot-pounds of torque.
Depending on its configuration, the D4 weighed between 9,970 and 10,250 pounds. It had a 61-inch wheelbase and rode on tracks, rather than tires. The operator steered the tractor by manually engaging and disengaging clutches to power, or brake, either the left or right track. It had a manual transmission containing five forward gears and one reverse gear.