Why a Caterpillar 955K Track Loader May Refuse to Move

[MikePhua]

The 955K and Its Mechanical Backbone
The Caterpillar 955K track loader was introduced in the late 1960s as part of Caterpillar’s evolution from cable-operated machines to fully hydraulic systems. Designed for rugged earthmoving, the 955K featured a direct-injection diesel engine, a torque converter transmission, and a clutch-brake steering system. With an operating weight around 30,000 pounds and a bucket capacity of roughly 1.5 cubic yards, it was a staple in construction, demolition, and quarry operations for decades.
Its drivetrain relied on a combination of planetary gear sets and steering clutches housed within the final drives. These components allowed the operator to steer by disengaging one side while applying a brake, a system that—while effective—requires regular maintenance and precise adjustment.
Common Symptoms of Drive Failure
When a 955K refuses to move, especially after sitting idle for months, the issue often lies within the steering clutch assemblies. In one case, the machine started and ran normally, but the right-side clutch failed to engage, rendering the loader immobile in that direction. This type of failure can stem from:

• Clutch discs sticking due to rust or oil contamination
  
• Brake bands worn or misadjusted
  
• Hydraulic actuation failure in later models with assist systems
  
• Linkage binding or disconnected control rods
  

If only one side fails to engage, the problem is likely isolated to that clutch pack or its control mechanism.
Diagnosing the Steering Clutch System
To pinpoint the issue:

• Start with the control linkage: Ensure the lever moves freely and actuates the clutch fork. Disconnect the linkage and manually move the clutch arm to feel for resistance.
  
• Check the clutch housing for oil contamination: The steering clutch should be dry. If oil is present, it may have leaked from the transmission or final drive seals, causing the clutch discs to slip.
  
• Inspect the brake band: If the brake doesn’t hold when the clutch is disengaged, the band may be worn or out of adjustment.
  
• Test the clutch engagement: With the engine off, rotate the track by hand while operating the clutch lever. Resistance should change as the clutch engages or disengages.
  

In some cases, the clutch discs may be rusted together from long-term storage. Applying penetrating oil and gently rocking the machine can help free them, though disassembly may be required.
Repair Strategies and Preventive Measures
If the clutch pack is contaminated or seized:

• Remove the clutch housing cover and inspect the discs and pressure plate.
  
• Replace worn or glazed discs with OEM or aftermarket kits.
  
• Clean the housing thoroughly and reseal any leaking input shafts.
  
• Adjust the clutch and brake linkages to factory specifications using feeler gauges and torque wrenches.
  

To prevent future failures:

• Operate the machine periodically, even if not in use, to keep components moving.
  
• Store the loader under cover to reduce moisture intrusion.
  
• Use high-quality lubricants and monitor fluid levels regularly.
  
• Log maintenance intervals and track clutch adjustments over time.
  

Conclusion
A Caterpillar 955K that won’t drive is often suffering from steering clutch issues, particularly on machines that have been parked for extended periods. By methodically inspecting the clutch linkage, housing, and brake system, operators can identify the root cause and restore mobility. With proper care and attention, these classic loaders can continue to serve reliably, even decades after their production ceased.