The Caterpillar D4 track-type tractor is a small bulldozer manufactured by Caterpillar Inc.
Caterpillar first introduced the RD4 in 1936,Orleman, Eric C. (2006) Caterpillar Motorbooks, St. Paul, Minnesota, page 38, as the diesel follow on to the successful CAT 30 gas model. The first RD4 weighed , and used Caterpillar's D4400 engine, an inline four-cylinder, with a bore and stroke.Leffingwell, Randy (1996) Classic Farm Tractors: History of the Farm Tractor Motorbooks International, Osceola, Wisconsin, page 70, In 1935 Caterpillar had started the naming convention of "RD" for diesel or "R" for regular gasoline, followed by a number to indicate the relative engine size. In 1937, the "RD" models began to be called just "D" models. At the time of introduction of the RD4, the D4400 engine produced about at the drawbar so the 4 was a relative indicator of engine power. The D4 U series was fitted with the more powerful D315 engine, and later engines used in the D4 brought further increases in power, but the number "4" was retainedindicating the tractor's position in the Caterpillar line-up rather than indicating engine power.
Version details 6U = Narrow gauge 7U = Wide Gauge Caterpillar RD4 - 1936-37 (4G) with 4-cylinder D4400 engineCaterpillar Chronicle by Eric C.Orlemann, published by MBI Caterpillar D4 - 1937-39 (4G) with 4-cylinder D4400 engine Caterpillar D4 - 1939-43 (7J) with 4-cylinder D4400 engine Caterpillar D4 - 1943-45 (2T) with 4-cylinder D4400 engine Caterpillar D4 - 1945-47 (5T) with 4-cylinder D4400 engine Caterpillar D4 - 1947-59 6U1 > 6U12781, 7U1-7U44307 Cat 4-cylinder D315 engine.Caterpillar Pocket Guide, by Bob LaVoie Caterpillar D4C - 1959-63Caterpillar by Eric Orlemann, pub by MBI, Caterpillar D4D - 1963-77 Caterpillar D4E - 1977-84 Caterpillar D4H - 1985-96 Caterpillar D4C SII -1990-93 Caterpillar D4C SIII - 1993
Tracked shovels The Caterpillar D4 was used as the base tractor for the Trackson built loader that was known as the T4 or Traxcavator shovel.
See also Caterpillar D5 Caterpillar D3 Caterpillar D2 Heavy equipment G-numbers Army cats. TM 9-2800 military vehicles SNL G151 light tractor
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