The History of Cat® D4 Dozer

Eighty-two years ago, we introduced the Cat® RD-4 track-type tractor – a machine that would eventually become the Cat D4.

The RD-4 (4G series), launched in 1936, was based heavily on the Cat R-4 spark-ignition gasoline powered track-type tractor, but without the gasoline engine. The RD-4 was powered by a Cat D4400, four-cylinder diesel engine that produced 41 horses’ worth of “Cat Diesel Power.”

A year later, the RD-4’s name was changed to the Cat D4. Other than the radiator, everything else on the tractor remained virtually unchanged. Other D4 models, based on this original design, were introduced in the next decade, including the 7J series from 1939 to 1942, the 2T series from 1943 to 1945, and the 5T series from 1945 to 1947. All were powered by the D4400 Diesel.

In 1947, a revised D4 (6U/7U) model was introduced, and it was equipped with the Cat D315 four-cylinder diesel engine rated at 48 belt-horsepower. Both engine variations on the D4 proved very popular in the marketplace, and with regular updates in horsepower remained on the product line all the way up to 1959.

The early D4 models were originally used for agricultural purposes. Today, they are one of the leaders in earthmoving. The D4 continued to evolve over time, and its DNA can still be found in today’s Cat D4K Series dozers.