35 Years. 175,000 Machines. 1 Big Innovation.

Thirty-five years ago, Caterpillar launched the H-series which brought the elevated sprocket or “high drive” concept to the Cat® medium track-type tractors (MTTT). In May, we celebrated the production of the 175,000 elevated sprocket MTTT – an achievement of manufacturing, innovation and customer-focus.

In 1985, the team introduced the H-series medium track-type tractors. For our customers, immediate benefits included improved durability and ease of service of the powertrain components. The medium tractors took advantage of one additional high drive benefit – the ability to extend the tracks forward or rearward to optimize tractor balance for unique applications. The D4H and D5H also combined a six-way adjustable, VPAT (Variable Power Angle Tilt) blade with the high drive undercarriage for the first time. These early high drive tractors pushed the levels of efficiency, productivity and ease of operation. All of these were – and still are – our Cat product advantage.

Since the H-series tractors were introduced, Caterpillar has continued to improve dozers and develop innovative solutions for customers. One of the first customers to operate a Next Gen D6 XE, a long-time earthmoving contractor, was astonished by the power and maneuverability and commented, “It is beyond what I thought was possible.”  There can be no better confirmation that today’s engineers are upholding the tradition of the original high drive tractors and going “Beyond Known Capabilities.”

Another way we’re helping customers with Cat’s Next Gen Dozers? A return to a family approach. Like the H-series, there are commonalities between medium dozers. For example, the D5, D6 and D7 share a common cab layout, which simplifies training for dealers and customers so operators can get up to speed faster. An added plus – the new cab is larger and more comfortable for operators. The new D7 also returns to the high drive configuration, leveraging scaled designs from the D8T. Even the nomenclature, D4-D7, are realigned with the numerical values used with the H-series.   

To commemorate the 175,000 MTTT high drive milestone, we produced three special edition tractors. Check them out:

Cat® D6 XE track-type tractors Cat® D6 XE track-type tractors
These Cat® D6 XE track-type tractors were finished in a unique dark gray and black paint scheme. One unit will go to Goodfellow Bros. Before being put to work, the tractor will be used as part of their own celebration of 100 years in business. The second unit will go to Holt of Texas. The Holt family’s history goes all the way back to Benjamin Holt inventing the track-type tractor in November of 1904. This D6 XE embodies 116 years of improvement since Holt’s original Caterpillar and will be shown at upcoming customer events.
 Cat® D6 XE track-type tractors  Cat® D6 XE track-type tractors
The third milestone tractor, a D6, is finished in traditional Caterpillar yellow, but with black tracks and a black blade. This special D6 will be going to Canada to Cat dealer Finning.
Cat® D6 XE track-type tractors Cat® D6 XE track-type tractors

The Elevated Sprocket: A Caterpillar Engineering Marvel

The original Cat elevated sprocket tractor was first introduced in 1977 on the D10. It revolutionized the earthmoving industry. The elevated sprocket allows machines to work harder and last longer while providing a much smoother operator ride. Today, it’s standard on medium and large Cat® track-type tractors. Who says you can’t have it all?


Cat® bulldozers help you move more material in less time. Fuel efficiency and features to make service and maintenance easier help you reduce your overall dozer owning and operating costs. Plus, factory integrated GRADE technology features help get work done even faster, from first pass to finish grade.

Learn More on Cat.com


Buckets or blades, tips or edges, rippers or side cutters – no matter the size, ground engaging tools have a direct effect on a machine’s ability to produce. Cat® Ground Engaging Tools (GET) are designed to offer performance and value differentiation for our customers.

Full Story