The Dart 600C Loader and Its Forgotten Legacy

[MikePhua]

The Rise and Decline of Dart Manufacturing
Dart Truck Company, once a respected name in off-highway and industrial equipment, operated out of Kansas City and specialized in heavy-duty loaders and haulers during the mid-20th century. The Dart 600C was introduced as part of their push into the large wheel loader market, competing with giants like Caterpillar’s 992 and LeTourneau’s electric-drive machines. While Dart never achieved the global dominance of its competitors, the 600C represented a bold attempt to carve out space in high-capacity earthmoving.
By the late 1970s, Dart’s loader production had slowed, and the company eventually faded from the mainstream equipment scene. Unlike Caterpillar or Komatsu, Dart lacked a global dealer network and long-term parts support, which ultimately limited the survivability of its machines in the field.
Terminology Annotation

• Nitrogen Assist System: A hydraulic suspension or lift system that uses pressurized nitrogen to augment fluid pressure, often found in boom or lift arm circuits.
  
• Offset Cab: A cab design positioned laterally from the machine’s centerline, intended to improve visibility but often complicating transport and shop access.
  
• Soft Shift: A transmission feature that modulates gear engagement to prevent harsh shifts at high speed, improving drivability and reducing wear.
  
• Electric Drive Loader: A loader powered by electric motors rather than a mechanical drivetrain, offering smoother torque delivery and reduced emissions.
  

Design Features and Engineering Choices
The Dart 600C was a massive machine, built for bulk loading in mining and quarry environments. It featured:

• A GM 12V149 diesel engine in some variants, known for its high RPM and distinctive sound
  
• Optional Cummins and Caterpillar powerplants depending on customer preference
  
• A nitrogen-assisted lift system that, when functional, provided smooth boom operation
  
• An offset cab that gave operators better visibility when loading trucks but created clearance issues in maintenance bays
  
• A rigid frame with planetary axles and high-capacity hydraulic cylinders
  

The nitrogen system, while innovative, was notoriously difficult to maintain. A full recharge could require up to nine standard nitrogen bottles, and leaks were common. When sealed properly, the system performed well, but many operators found it temperamental in cold climates or under heavy cycling.
Operational Challenges and Maintenance Realities
Despite its raw power, the Dart 600C was plagued by reliability issues. The transmission lacked a soft shift mechanism in early models, leading to gear damage if operators shifted at high speeds. The hydraulic system required frequent resealing, and parts availability became a major obstacle after Dart ceased production.
Owners often resorted to fabricating replacement components or scavenging parts from retired machines. Some fleets retrofitted the loaders with alternative engines or rebuilt hydraulic systems using generic seals and hoses. The offset cab, while praised by some for visibility, made the machine awkward to maneuver in tight spaces and difficult to transport.
A Story from the Field
In the 1980s, a mining operation in Queensland operated a fleet of Dart 600Cs, including one unit retrofitted with a GM 12V149 engine. The machine was a favorite among operators for its digging power and aggressive stance. However, the nitrogen system failed repeatedly, and the company eventually converted the lift circuit to a conventional hydraulic accumulator setup. The modified loader continued working for another decade before being replaced by Caterpillar 992Cs.
Rare Electric Variant and Competitive Ambitions
Dart also experimented with an electric-drive version of the 600 series, designated the DE620. This model featured two electric motors—one mounted to the front axle input and one to the rear—mirroring LeTourneau’s approach to electric loaders. The DE620 was intended to reduce fuel costs and simplify drivetrain maintenance, but it never reached mass production. Only a handful of units were built, and documentation is scarce.
The electric variant was part of Dart’s attempt to compete with LeTourneau in the mining sector, where electric loaders were gaining traction due to their torque characteristics and reduced emissions. However, without a strong dealer network or long-term support, Dart’s electric ambitions faded quickly.
Parts Availability and Restoration Potential
Today, finding parts for the Dart 600C is a challenge. Some operators have located stockpiles of components—rims, tires, transmissions, axles, and cylinders—often enough to rebuild multiple machines. These caches are typically held by private collectors or small salvage yards in Canada and the U.S.
For restoration:

• Use GM or Cummins rebuild kits for engine overhauls
  
• Retrofit hydraulic cylinders with modern seals and rod coatings
  
• Replace nitrogen systems with hydraulic accumulators or spring-assist setups
  
• Fabricate cab panels and glass using custom templates
  
• Source planetary axle components from compatible off-highway trucks
  

Industry Trends and Lessons Learned
The Dart 600C serves as a cautionary tale in equipment design: innovation without long-term support can leave even powerful machines stranded. While the loader offered impressive digging force and visibility, its complex systems and lack of parts support limited its lifespan.
In contrast, Caterpillar’s 992 series, introduced in the same era, continues to receive factory support and aftermarket upgrades. The success of the 992C and its successors highlights the importance of dealer infrastructure and standardized components.
Conclusion
The Dart 600C was a bold, if flawed, entry into the world of heavy wheel loaders. Its offset cab, nitrogen-assist system, and electric-drive variant reflected a willingness to innovate, but without sustained support, these features became liabilities. For collectors and restoration enthusiasts, the 600C remains a rare and challenging project—one that rewards mechanical ingenuity and historical appreciation. In the broader context of earthmoving history, Dart’s legacy is one of ambition, experimentation, and the hard lessons of industrial survival.