The Caterpillar D10 heavy tractor

On its introduction in 1977, the Caterpillar D10 raised quite a few eyebrows: firstly because of its sheer size and secondly the odd configuration of the undercarriage.

The concept of an elevated sprocket drive wasn’t a new one and dated back to C.L.Best’s model 45 “Humpback” of 1914 and Cletrac’s F-series tractor of 1934.

It wasn’t until Caterpillar introduced its D10 that the idea again came to public attention.

Following the introduction of the D10, the entire Caterpillar range of track type tractors have received the elevated sprocket design at one time or another, with the exception of the D3.

It is interesting to note that none of Caterpillar’s competition offers a machine in this drive configuration.

Caterpillar began serious design development of what was to become the D10 in 1969 in response to requests for a tractor larger than the (then) current D9G.

In fact the idea of a tractor larger than the D9 was mooted as far back as 1955!

Beginning in 1973, several test “mules” were constructed to prove some of the designs and to iron out the bugs that invariably appear in a new machine, especially one as large and radical as the D10.

Test machines were sent to selected contractor’s jobs and also to Caterpillar’s Arizona proving ground where some were worked to destruction in order to determine component life expectancies.

Officially unveiled in September 1977, first deliveries of the new machine did not take place until 1978.

Following a few ‘meltdowns’, a revision was made to the D10’s exhaust system quite early in production. This change replaced the single large exhaust pipe with two separate stacks, one on either side of the bonnet. This reduced heat buildup in the turbocharger area and as a consequence also improved the machines’ exhaust back-pressure.

Consideration had obviously been given to this problem during design as the machine came delivered from the factory with a fire suppression system in the engine bay.

Sales of the D10 were very strong and at one point Caterpillar had a quite a waiting list for new machines, the demand was that great.

D10s could be found in most segments of the industry, including quarry, mining and large roading or subdivisional works.

Mining contractors particularly liked them because they could rip material that formerly had to be blasted.

Production of the 84W series D10 was discontinued in 1986 following a design revision that resulted in the D10N.

Subsequent versions of the machine have included the D10R and the current production version, the D10T.

The Caterpillar D10 Described

As this article is a retrospective look back, we will be examining the first production model of the machine, the 84W series.

It was powered by a 700 horsepower Caterpillar D348TA V-12 twin turbocharged diesel engine.

This was mated with a Caterpillar barrel-type planetary powershift transmission.

One of the principal considerations when designing the D10 was ease of servicing and to this end the transmission or final drives could be extracted very easily in just over an hour due to the modular design of the tractor.

Another feature (since copied by some other manufacturers) was the independent bogies that held the bottom track rollers. These allowed the tracks to wrap over an obstacle rather than ramp up it, reducing point loading on the tracks and adding to the machine’s traction.

There was a track idler at both ends of the track frame and a very large hydraulically adjusted recoil cylinder maintained track tension.

Track frames were entirely independent of the final drives and were held in place by a very substantial pivot shaft at the rear and a conventional equalizer bar at the front allowing track frame oscillation.

This arrangement prevented any shock loads being transmitted to the machine’s final drives.

Isolation mounted from the tractor frame was the operator’s compartment.

This featured a suspension seat angled off at around 30 degrees to the right to allow easy visibility to the ripper and blade.

The entire interior was very well laid out and obviously the folks at Caterpillar had put a lot of thought into its design.

All the control levers featured short throws and were closely grouped to minimize operator fatigue. No pedals or levers penetrated the floor plate allowing easy access in and out of the cab with the added benefit of heat, dust and noise reduction.


Caterpillar offered several attachments to outfit the D10.

Blades included the 10S straight blade, 10U full U bulldozer and the 10C that was a cushioned blade specifically designed for pushing scrapers.

Angle blades were not offered nor, apparently, a logging winch.

The most common ripper fitted was the fully adjustable single shank type with hydraulic pin puller – a multi shank model was also available.

A very specialized impact ripper was offered for a time but seems to have been discontinued.

You could have a variety of track shoe widths and a choice of open ROPS or fully enclosed ROPS cab with all the trimmings.

The New Zealand Connection

The first New Zealand contractor to receive a D10 was Fred Willetts followed closely by Baker Construction who eventually received two. The machines were put to work at Twizel & Pukaki on the hydroelectric schemes and gave a very good account of themselves in the often difficult conditions found on this project.

The early D10’s were a real ‘operator’s machine’ and are spoken of very highly by all who operated them.

Including private imports there have been nine Caterpillar D10’s (84W series) imported into New Zealand.

For the Model Collector

For once there is quite a bit of choice when it comes to models of our featured subject.

Conrad, Norscot and Classic Construction Models (CCM) have all produced models of the D10 to 1:50th scale.

Conrad’s models can be an early D10 with the single large stack, as a later D10 with the twin stacks and has also been issued as a D10N.

Norscot’s D10 was issued as a D10N and latterly a D10T but is crude in comparison to the Conrad model.

The CCM model represents an early single stack D10 and was issued as a ‘push-cat’ with the 10C blade and open ROPS while the second issue came with a semi-U blade, ripper and ROPS cab.

CCM’s model is head and shoulders above the other two in terms of detail and quality but not surprisingly, it is also the most expensive at around NZ$275 apiece.

For the budget conscious there is also a 1:70th scale model produced by Joal.

Brief Specifications – Caterpillar D10 (84W series)

Engine:                      Caterpillar D348TA, twin turbocharged, aftercooled V-12 diesel rated at 700 flywheel horsepower @ 1800 rpm

Transmission:         Caterpillar full powershift planetary transmission with 3 fwd and 3 rev speeds

Top Speed:               7.2 mph

Steering:                    Multiple disc clutch

Track Gauge:            9’ 6”

Std.Track Shoe:       28”

Rollers per side:      8 mounted on 4 bogies

Length:                      31’ (with blade & ripper)

Width:                         18’ (with 10S blade)

Height:                       14’ 10” (to top of ROPS)

Operating Weight:   100 tons with blade & multi shank ripper

The Caterpillar D10 tractor

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