Komatsu Dozer Models Explained

The Komatsu D20 and D21 small dozer line is the only light substantial dozer currently manufactured as new by a major equipment company. The weight on these dozers ranges 8,000-9,000 # depending on options. They can be hauled on a 12,000 GVW trailer behind a pickup with a class 5 hitch.  They are an excellent dozer choice for someone who has a homestead type property and wants to put in their own improvements, a remote site work machine capable of building an airstrip, a residential contractor that needs to work around tight spaces, or just someone who always wanted a dozer to play with. They will do a lot of work, you just have to take your time. For this size dozer you basically have few purchase choices other than older JD and Case 350 models or the Komatsu. Komatsu company, while not well known in Alaska, is a huge construction machinery company with worldwide distribution. They have a huge line of dozers from largest made to smallest and parts are readily available. These are fantastic little bulldozers and we have dozens of testimonials to their use and efficiency.  The dozers we obtain for sale come in 2 basic models and track configurations.

There are 2 model numbers that show transmission type.

D20 = direct drive transmission. This is a standard shift, where you operate a foot clutch and shift with a lever mounted on the floor. Very similar to a standard shift truck and same benefits. Simple, long lasting and more power to the running gear. Very durable and idea for remote location use. The 3rd forward speed is very fast for overland travel.

D21 = power shift transmission or hydrostatic. This allows shifting without using a clutch. You still have to shift to change direction and speed, but the lever is mounted on the side by armrest. There is still a clutch if you need it for close in work. 2 forward speeds /2 reverse. U pattern with neutral in the center forward. This provides a more open cab design than the direct drive models. Faster operation is one benefit.

There are 2 letter designations after the model number that show track type

A Model = Standard track width. On the factory “A” model the shoes are a 12″ (300mm) single grouser with 5.1 psi ground pressure. Blade width is just over 7′. On the models that we convert the shoes, we install a slightly wider 13.5″ single grouser for 4.75 psi ground pressure. 

P Model = wide track. On the factory “P” model the shoes are 20″ (510mm) pyramid or swamp type shoes with 3.4 psi ground pressure. Some have grouser bar welded to the top for additional traction. These are an excellent low ground pressure pad and are self cleaning and will run in snow without plugging. They are rough riding on rocky ground, do not provide as much traction as the single grouser shoes and tend to break in hard ground applications. Blade width on the “P” model is 8′-4″ and angles to 8′.

We can convert the “P” models to an “A” model by changing out the track shoes to an improved 13.5″ (340mm) single grouser shoe or the factory spec 20″ single grouser shoe. The 13.5″ shoe increases the ground pressure to 4.75 psi but you have the advantage of increased traction, keep the larger blade of a “P” model and the tracks are more offset from the machine providing a wider stance and more stability. We believe this modification gives you an excellent machine/track combination and is only available from us. We have the shoe plates and bolts in stock to do whatever you prefer.


D21P – is a powershift wide track
D20P – is a direct drive wide track
D21A – is a powershift narrow track
D20A – is a direct drive narrow track

The only other model designation is the -5, -6 or -7
Models ending in -5 are pre 1985
Models ending in -6 are 1985-1992
Models ending in -7 are 1992-2000
Models ending in -8 are 2000 or newer

There are also some -7 models produced after 1997 that have a single lever blade control and the 2 speed in the directional joystick.

The -7 had some significant improvements to the engine and introduced the joystick steering control option and in models after 1997 a single lever blade control.

The -8 models have the latest refinements. The most significant is the ROPS canopy as standard equipment. They are typically the high end contractor models. The -8 models are hard to find with the joystick steering that is popular in North America.

All can be outfitted with an aftermarket Roll Over Protection System canopy to replace the fiberglass rain canopy. We stock all steel canopies.  (ROPS INFO).

Click here to download the Komatsu D21-7 brochure

THE D31 IS THE LARGER BROTHER OF THE D21-  Weighing in at close to 16,000#  there are no direct drive D31 models, all are powershift. The  “P” models are a 24″ wide pad with 9′ blade, the “A” models are a standard pad approx 13″ and 7.5′ blade. They are all powershift and the D31-18 models are lever steer, the D31-20 are typically single lever joystick steering. You can convert the “P” and “A” models to 16″ track width if desired.


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