Diagnosing Steering Failures on the Caterpillar 951C Track Loader

[MikePhua]

The 951C and Its Mechanical Steering System
The Caterpillar 951C track loader was introduced in the mid-1970s as part of Cat’s evolution from cable-operated to fully hydraulic machines. With an operating weight of roughly 30,000 lbs and powered by a Cat 3304 diesel engine, the 951C was built for rugged earthmoving, land clearing, and material handling. Unlike modern hydrostatic loaders, the 951C uses a mechanical transmission with clutch-brake steering—an arrangement that relies on friction discs, brake bands, and linkages to control track movement.
Steering problems in the 951C often stem from wear, misadjustment, or hydraulic imbalance in the steering clutch and brake assemblies. Because the system is mechanical-hydraulic hybrid, troubleshooting requires both fluid diagnostics and physical inspection.
Symptoms of Steering Malfunction
Operators may encounter:

• One track failing to disengage or brake
  
• Loader turning only in one direction
  
• Steering levers feeling loose or offering no resistance
  
• Audible grinding or squealing during turns
  
• Machine creeping forward even with one lever fully pulled
  
• Brake pedal having excessive travel or no effect
  

These symptoms suggest that either the steering clutch is not releasing properly or the brake band is not engaging with sufficient force. In some cases, both systems may be compromised simultaneously.
Understanding the Clutch-Brake Steering Layout
The 951C uses a dry steering clutch system paired with mechanical brake bands. Each track is controlled by a lever that:

• Disengages the clutch to stop power to the track
  
• Applies the brake band to halt track movement
  
• Allows the opposite track to continue driving, turning the machine
  

The clutch is spring-loaded and released hydraulically or mechanically depending on configuration. The brake band wraps around a drum and is activated by linkage or pedal force.
Common Causes of Steering Failure
Several issues can lead to steering problems:

• Worn clutch discs
  Friction material may be glazed, cracked, or missing, reducing disengagement effectiveness.
  
• Oil contamination in dry clutch housing
  Leaking seals can allow transmission or final drive oil into the clutch pack, causing slippage.
  
• Stretched or broken brake bands
  Bands may lose tension or crack, especially if overheated during prolonged use.
  
• Linkage misalignment or wear
  Steering levers and rods may have excessive play, preventing full clutch release or brake engagement.
  
• Hydraulic imbalance
  If the clutch release is hydraulic, low pressure or air in the lines can cause inconsistent response.
  
• Frozen or seized pivot points
  Rust or debris can lock up the brake pedal linkage or clutch arm, especially in machines stored outdoors.
  

A technician in Texas once found that a 951C wouldn’t steer left due to a broken return spring on the left clutch arm. The clutch remained partially engaged, and the brake couldn’t overcome the torque. Replacing the spring and adjusting the linkage restored full steering.
Inspection and Repair Strategy
To diagnose and repair:

• Remove the side covers and inspect clutch pack condition
  
• Check for oil contamination—dry clutches should be clean and dusted, not oily
  
• Measure brake band thickness and tension
  
• Inspect all linkage points for wear, rust, or misalignment
  
• Verify hydraulic pressure if applicable
  
• Adjust clutch release and brake engagement per service manual specs
  
• Replace worn springs, pins, and bushings as needed
  

If oil is found in the clutch housing, the transmission input seal or final drive seal may need replacement. This requires splitting the machine or removing the steering clutch assembly.
Preventive Maintenance and Operator Tips
To extend steering system life:

• Avoid riding the steering levers—use them only when turning
  
• Keep the clutch housing clean and dry
  
• Grease all linkage points monthly
  
• Inspect brake band tension quarterly
  
• Drain and refill transmission and final drive oil annually
  
• Store the machine under cover to prevent moisture intrusion
  

Some owners retrofit inspection ports or install magnetic drain plugs to monitor clutch housing contamination.
A Story from the Field
In 2021, a land-clearing crew in Georgia reported that their 951C would only turn right, even with full left lever engagement. After removing the left clutch housing, they discovered oil-soaked friction discs and a cracked brake band. The final drive seal had failed, allowing gear oil to flood the clutch. After replacing the seal, clutch pack, and brake band, the loader returned to full function. The crew later added a weekly inspection checklist to prevent recurrence.
Conclusion
Steering problems in the Caterpillar 951C are often mechanical in nature, rooted in clutch wear, brake failure, or linkage misalignment. With careful inspection, proper adjustment, and preventive care, these issues can be resolved and avoided. In legacy iron like the 951C, steering isn’t just about turning—it’s about understanding the dance between friction, force, and timing. When the clutch releases cleanly and the brake bites true, the machine responds like it was built to.