Caterpillar D9
Cat D9G at EM wd 2011 - IMG 0517
Caterpillar D9G at the East Midlands and Link Club Working Day 2011
Model history
Model introduced Unknown
Model discontinued Unknown
Model status Unknown
Engine Specification
Engine make Caterpillar
Fuel type Diesel
Power hp 474
Power kW 353
Cooling system Water
Transmission Details
Transmission type Unknown
Drive tracked
Linkage Category Unknown
Other info
Factories USA
Plow rating Unknown
Web site
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The Caterpillar D9 is a large track-type tractor series designed and manufactured by Caterpillar Inc..

Though it comes in many configurations it has usually been sold as a bulldozer equipped with a detachable large blade and a rear ripper attachment.

The D9, with 474 hp (353 kW) of gross power and an operating weight of 49 tons, is in the upper end, but not the heaviest, of Caterpillar's track-type tractors, which range in size from the D3 77 hp (57 kW), 8 tons, to the D11 935 hp (697 kW), 104 tons.

The size, durability, reliability, and low operating costs have made the D9 one of the most popular large track-type tractors in the world, with the Komatsu D275A as one of its most direct competitors.

Until the introducing of the D10 in 1977 at a dealer meeting, the D9H was the largest conventional bulldozer built by Caterpillar.

The size, power and weight of the larger track-type tractors dictate that they are used primarily for major projects. The D9 is most commonly found in use in construction, forestry, mining, waste, and quarry operations.

Engineering and technical developmentEdit

The D9 is a series of heavy tracked-type tractors, propelled by Caterpillar tracks and usually used as bulldozers.

The D9 has undergone several generations of engineering enhancements. Each new model is denoted with a suffix letter to indicate version added to D9 like D9E,D9G,D9H,D9L,D9N,D9R and the current D9T.

Time lineEdit

Caterpillar D9

Early D9 in the Auto und Technik Museum, Sinsheim Germany

  • 1954 - prototype D9X.10
  • 1955 - The 286 hp (213 kW) D9 was introduced to compete against the Euclid TC-12 which had more horsepower. The D9 would come equipped with a 1,473 cid D353 which would power the D9 right up until the 1980 introduction of the D9L.
  • 1956 - The D9 got a boost up to 320 hp (240 kW).
  • 1959 - The new 335 hp (250 kW) D9E would replace the original D9 model.
  • 1961 - The legendary 385 hp (287 kW) D9G would appear and be in production for the next 13 years. Over its 13 year life the D9G would be the main crawler on many job sites testifying to its sturdiness and design.
  • 1965 - In America, the west coast businessman Buster Peterson hooked up a pair of D9Gs to push the largest wheeled tractor scrapers built. In 1986 Caterpillar Inc. bought the rights to this concept and thus the 770 hp (570 kW) DD9G was created, the D stands for Dual D9G. Peterson also built the first SxS D9G which has 2 D9Gs side-by-side pushing a 24 foot wide bulldozer blade. In 1969 Cat introduced this new SxS D9G.
  • 1974 - The improved 410 hp (310 kW) D9H was introduced to replaced the D9G. The D9H is still the more powerful conventional track-type tractor in company history. The DD9H and the SxsD9H would soon follow.
  • 1980 - The 460 hp (340 kW) D9L was introduced. The unit had the same elevated drive sprocket undercarriage that the larger D10 had. But it is noted that in the time period of 1970-71 a Prototype D9G was built with an elevated drive sprocket undercarriage . A picture of one can be found on page 95 in a book called "Caterpillar Chronicle" by Eric Orlemann. The D9L was the most powerful D9 in history, with flywheel power of 460 hp.
  • 1987 - The 370 hp (280 kW) D9N replaced the D8L.
  • 1987 - The D9L was replaced by the 520 hp (390 kW) Caterpillar D10N.
  • 1988 - Caterpillar produced their 25,000th elevated drive sprocket track-type tractor which a D9N.
  • 1996 - The 405 hp (302 kW) D9R replaced the D9N.
  • 2004 - The 410 hp (310 kW) D9T replaced the D9R.


Main article: Caterpillar D9L

The D9L was the first variation of the D9 to employ elevated drive sprocket design in which the drive sprocket is elevated above the track, and not on the ground. The elevated drive sprocket gives the "belly pan" more ground clearance. The elevated drive sprocket undercarriage is a modular design. To repair the machines you break down the tracks and pull the drive sprockets out. As a result you can pull the powershift transmission out the rear.


Caterpillar D9T - IMG 8550

Caterpillar D9T fitted with a single shank Ripper (inverted for transport)

Main article: Caterpillar D9T

The D9T has a Caterpillar ACERT diesel engine. The current versions are the D9R and the D9T models, but older models such as the D9N and D9L are still common. The L, N, R and T models of the D9 are visually very similar, differing primarily in the design of their internal systems. The D9T's main difference from the D9R is the installation of the new Cat C18 ACERT engine.


The D9's primary working tools are the blade, affixed to the front and controlled by 6 hydraulic arms, and the optional ripper, which can be attached to the back. The blade is mainly intended for earthmoving and bulk material handling: pushing up sand, dirt and rubble. It also can be used to push other heavy equipment such as earthmoving scraper pans, and in military applications, main battle tanks.

The dozer blade usually comes in 3 varieties:

  1. A Straight Blade ("S-Blade") which is short and has no lateral curve, no side wings, and can be used for fine grading.
  2. A Universal Blade ("U-Blade") which is tall and very curved, and has large side wings to carry more material.
  3. A "S-U" combination blade which is shorter, has less curvature, and smaller side wings. This blade is typically used for pushing piles of large rocks, such as at a quarry.

Like many other bulldozers, the D9 can be fitted with different blades (such as size-9 SU blade and Universal blade) or other devices such as mineplows.

The rear ripper is intended for use in loosening rocky ground and ripping out larger stones. It can also break frozen ground and excavate small ditches. The ripper can be replaced with a multi-shank ripper, allowing the bulldozer to comb the ground.

Military applicationsEdit

Caterpillar Inc. does not manufacture a military version of the D9 per se, but the attributes that make the D9 popular for major construction projects make it desirable for military applications as well, and in this role - with Israeli modifications and armour - it has been particularly effective for the Israel Defense Forces (IDF) and later for the United States armed forces (the Marine Corps and the US Army) in Iraq.[1]

The US army used D9 bulldozers to clear forest in the Vietnam war but after the war they were replaced with smaller and cheaper Caterpillar D7G bulldozers. D7G dozers are still very common in US combat engineering battalions, but there is a resurgent high demand to replace the lighter D7Gs with the newer and more heavily armoured D9s.

See alsoEdit

Preceded by
Caterpillar Bulldozers Succeeded by


Wikipedia for base article (For military applications see Wikipedia article)

  1. Video of US Army / US Marine teams working with civilian contractors from KBR Heavy Equipment Transport, using D9s at Ar Rutbah to build a large defensive berm

External linksEdit

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