Caterpillar D9 The Caterpillar D9 is a large track - type tractor designed and manufactured by Caterpillar Inc . It is usually sold as a bulldozer equipped with a detachable large blade and a rear ripper attachment . The D9 , with 354 kW ( 474 hp ) of gross power and an operating weight of 49 tons , is in the upper end of Caterpillar ' s track - type tractors , which range in size from the D3 57 kW ( 77 hp ) , 8 tons , to the D11 698 kW ( 935 hp ) , 104 Tonne . The size , durability , reliability , and low operating costs have made the D9 one of the most popular large track - type tractors in the world . The Komatsu D275A is one of its most direct competitors . Engineering and technical description . The D9 is a series of heavy tracked - type tractors , propelled by Caterpillar track s and usually used as bulldozers . The series began in 1954 with a prototype tractor called the D9X . Ten D9X prototype models were built in 1954 . In 1955 , the D9 was introduced to compete against the more powerful Euclid TC - 12 . The D9 came equipped with a 1 , 473 cid D353 which powered the D9 right up until the 1980 introduction of the D9L . In 1956 the D9 had its engine power raised to . The new D9E replaced that model in 1959 . Two years later , in 1961 , the legendary D9G was introduced , that remained in production for 13 years . Over its 13 - year life the D9G became the main crawler on many job sites , testifying to its sturdiness and design . In 1965 , West Coast businessman Buster Peterson hooked up a pair of D9Gs to pushload the largest wheel tractor scrapers built . In 1986 Caterpillar bought the rights to this concept and thus the DD9G was created ( D stands for Dual D9G ) . Peterson also built the first SxS D9G which has two D9Gs side - by - side , pushing a wide bulldozer blade . In 1969 , Caterpillar introduced this new SxS D9G . In 1974 , the improved D9H was introduced to replace the D9G . The D9H is still the more powerful conventional track - type tractor in company history . The DD9H and the SxsD9H would soon follow . In 1980 , the D9L was introduced . The unit featured the same new type of elevated - sprocket undercarriage as was used in the larger D10 . 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 new undercarriage design reduced strain and shock loads on the final drives and gave the " belly pan " more ground clearance . The elevated - drive - sprocket undercarriage is a modular design . To repair the machines one breaks down the tracks and pulls the drive sprockets out . As a result , one can pull the powershift transmission out the rear . The D9N replaced the D8 L in 1987 . In 1988 , Caterpillar produced their 25 , 000th elevated - drive - sprocket track - type tractor , a D9N . The D9R replaced the D9N in 1996 . The D9T replaced the D9R in 2004 . The D9T has a low - emissions ACERT diesel engine . The current model is the D9T ; however , older models such as the D9R , D9N , and D9L are still commonly used . The L , N , R and T models of the D9 are visually very similar , differing primarily in the design of their internal systems . The D9L was replaced by the D10N in 1987 . The D9N replaced D8L in 1987 . The main difference between the D9T and the D9R is the installment of the new Cat C18 ACERT engine . The D9L is the most powerful D9 in history , with a flywheel power of 460 hp . The D9L is also the heaviest D9 in history at 130 , 000 lbs . The D9 ' s primary working tools are the blade , affixed to the front and controlled by six hydraulic arms , and an 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 tank s . The dozer blade usually comes in three variants : Like many other bulldozers , the D9 can be fitted with other devices such as mine plow s . 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 . 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 . Military applications . 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 armor - it has been particularly effective for the Israel Defense Forces ( IDF ) and also used by KBR in Iraq . 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 D7 G bulldozers . D7G dozers are still very common in US combat engineering battalions , but there is an series of oft - recurrent suggestions to replace the lighter D7Gs with the newer and more heavily armored D9s .