Iron Profile: The Caterpillar D8 Through History

Few pieces of equipment are more representative of the history of Caterpillar than their D8 track-type tractors. This family of machines has been an integral part of the Caterpillar line from its farm and agricultural roots to the construction and mining equipment powerhouse it is today.

First introduced in 1935 as the RD8, this tractor was immediately popular for its balance of size and power. As the years went by, a multitude of attachments and modifications would be made available from both Caterpillar and allied equipment manufacturers. This included products such as cable-operated bulldozer blades, canopies, push blocks, pipelayer cranes, and towed scrapers. Each year saw successive improvements in design, features and horsepower.

As the construction industry grew hungry for machines to build America, the D8 tractor catered to their desires with reliable performance. Military versions of the D8 found their way to the theaters of World War II and provided critical support for the construction needs of American forces.

HISTORIC D8 HIGHLIGHTS:

The RD8 debuts in 1935. Based on a Caterpillar Seventy-Five with a little more horsepower, it wouldn't be long before it was updated with the D13000 six-cylinder diesel engine, pushing it to 95 drawbar horsepower and 108 belt horsepower. Its operating weight was 50,025 lbs.

By the 1950s the D8 would have style changes to the body and the ever-reliable D13000's horsepower was increased 150 at the drawbar. With thousands of units in the field, the D8 dropped the "R" in its designation and was a top seller in Caterpillar's stable.

Before the larger D9 was created, any demands for a more powerful tractor were sometimes met with unique solutions. The Twin D8 above was one of only three developed by Peterson Tractor's Special Equipment Services between 1949 and 1951. Tested with a variety of attachments, one would eventually be equipped with a custom 22-foot wide bulldozer blade. Peterson engineers would directly influence Caterpillar Research more than any other outside source at the time.

The D8H in 1969, shown here with a standard hydraulic bulldozer blade.  Some of the many other attachments available were front and rear push blocks allowing multiple D8s to push equipment together end-to-end, and a three-shank ripper for breaking up rock on a job site.

A D8K Track-Type Tractor, circa 1974. The machine now boasted 300 flywheel horsepower provided by the Cat D342 turbocharged, fuel-injected, six-cylinder diesel engine. Improvements had been made all around; the frame made thicker for more durability, a higher load handling transmission, and a larger radiator for more efficient cooling. This unit is shown with optional ROPS (Roll Over Protection System) Modular Cab, heavy-duty radiator guard, track roller guards, hydraulic control, 8S Bulldozer and multishank ripper.

In 1981 Caterpillar introduced a completely redesigned tractor with the D8L. The most obvious of these improvements was the elevated final drives and sprockets. This system, first introduced In the D10 tractor, allowed the final drives, clutches and brakes to be free of the loads and stress common to the old design. The ROPS and cab were now standard, and the D8L was now the most powerful in the D8 lineage with the 335 flywheel horsepower 3408 turbocharged, V-8 diesel engine.

Caterpillar's current version is the D8T, released in 2004. It features all of the most modern engineering that makes it one of the best bulldozers in the world. The engine is the Cat 15 ACERT six-cylinder diesel, producing a maximum 364 horsepower. Operator controls are ergonomic, responsive, and precise. The powertrain benefits from a century of Caterpillar experience, and its differential steering and power shift transmission allow fine control of an impressive amount of power.

Over the decades of the D8's lifetime, innovations in its design have always been toward optimized operator comfort and maximized production capability. The D8 was quickly accepted as the industry standard for large earth moving applications, and their durability and continuing popularity is easily verified by the number of these tractors still in use today in every type of environment. What the future holds for this series of tractors can only be guessed, but we are be sure the D8 will maintain legendary status.