Drawbar Pull and Performance of the Caterpillar 951B Track Loader

[MikePhua]

The Evolution of the 951B in Caterpillar’s Lineage
Caterpillar introduced the 951B track loader in the early 1970s as a successor to the original 951 series, refining its design for better power delivery, hydraulic responsiveness, and operator comfort. The 951B was part of a broader movement by CAT to modernize its crawler loaders, integrating more robust undercarriages and improved engine-transmission pairings. With a rated engine output of approximately 85 horsepower, the 951B was positioned between the lighter 941 and the heavier 955, making it a versatile choice for contractors handling excavation, loading, and land clearing.
Caterpillar, founded in 1925, had by then become a global leader in earthmoving equipment. The 951B contributed to CAT’s dominance in the track loader market, with thousands of units sold across North America, Europe, and Australia. Its popularity stemmed from its balance of power, maneuverability, and serviceability—qualities that made it a staple on construction sites and in forestry operations.
Understanding Drawbar Pull and Its Relevance
Drawbar pull refers to the horizontal force a machine can exert at its hitch point, typically measured in pounds or kilonewtons. It’s a critical metric for evaluating a track loader’s ability to tow, push, or overcome resistance during dozing or ripping tasks. For the 951B, drawbar pull is not explicitly listed in many modern spec sheets, but comparative analysis with similar machines of the era provides a reliable estimate.
Terminology annotation:
- Drawbar Pull: The maximum horizontal force a machine can exert at its rear hitch, used to assess towing and pushing capability. - Direct Drive (DD): A transmission type where engine power is mechanically transferred without torque converters, offering higher efficiency. - Powershift Transmission: A hydraulic transmission allowing gear changes without clutching, common in heavy equipment for smoother operation.
Based on comparisons with the Caterpillar D4D dozer, which had slightly less horsepower (80 hp) and a drawbar pull of 13,550 lbs in first gear, the 951B likely achieves similar figures. A direct-drive D5 of the same vintage, with 93 hp, produced 17,330 lbs of drawbar pull in first gear. Given the 951B’s 85 hp rating and similar drivetrain characteristics, its drawbar pull is estimated to fall between 13,000 and 15,000 lbs under optimal conditions.
Weight and Traction Considerations
The operating weight of the 951B is approximately 10 tons (20,000 lbs), which plays a significant role in traction and drawbar performance. Heavier machines generate more ground pressure, improving grip on loose or uneven terrain. However, excessive weight can also increase fuel consumption and reduce maneuverability.
Operators often balance weight and traction by adjusting ballast, track tension, and undercarriage wear. Proper track maintenance ensures consistent drawbar performance, especially when working in clay, sand, or gravel.
Recommendations for optimizing traction:

• Maintain correct track tension to prevent slippage
  
• Use grousers with appropriate depth for the terrain
  
• Inspect sprockets and rollers for wear that may reduce power transfer
  
• Avoid overloading the bucket, which shifts weight forward and reduces rear traction
  

Transmission Type and Its Impact on Pulling Power
The 951B was available with both direct-drive and powershift transmissions. Direct-drive models typically deliver higher drawbar pull due to reduced power loss in the drivetrain. Powershift versions offer smoother operation and better control but may sacrifice some raw pulling force.
Operators using the 951B for towing or pushing should consider:

• Operating in first gear for maximum torque and drawbar pull
  
• Avoiding sharp turns under load, which can reduce traction and increase wear
  
• Monitoring transmission temperature during prolonged pulling tasks
  

Terminology annotation:
- Torque: Rotational force produced by the engine, critical for low-speed pulling. - Gear Ratio: The relationship between engine speed and wheel speed, affecting torque and drawbar pull. - Transmission Temperature: A key indicator of drivetrain stress, especially during heavy-duty operations.
Field Anecdotes and Practical Insights
One operator in New Zealand shared that his 951B was used for land clearing and stump removal, often pulling heavy root balls across uneven terrain. He noted that the machine performed best in first gear with moderate throttle, allowing the tracks to maintain grip without spinning. After switching to a direct-drive model from a powershift version, he observed a noticeable increase in pulling capacity and reduced fuel consumption.
Another technician recalled using a 951B to tow a disabled scraper across a quarry. With careful gear selection and proper ballast, the loader managed the task without overheating or track slippage—a testament to its underrated pulling power.
Maintenance and Performance Preservation
To maintain optimal drawbar performance, regular service is essential. Key maintenance tasks include:

• Checking final drive oil levels and replacing every 500 hours
  
• Inspecting track pads and grousers for wear
  
• Lubricating pivot points and linkage assemblies
  
• Monitoring engine RPM and transmission response under load
  

Operators should also consider installing a drawbar force gauge for real-time feedback during towing operations. This tool helps prevent overloading and identifies traction loss before damage occurs.
Conclusion
The Caterpillar 951B may not have modern electronics or digital diagnostics, but its mechanical strength and drawbar capability remain impressive. With an estimated pulling force exceeding 13,000 lbs, it holds its own against comparable dozers and loaders of its era. Through proper gear selection, maintenance, and terrain awareness, operators can unlock the full potential of this classic track loader. In the world of vintage iron, the 951B proves that raw power and smart technique still move mountains.