Diagnosing Steering Brake Issues on the CAT 931 Track Loader: Dry Clutches, Adjustment Techniques, and Field Fixes

[MikePhua]

Overview of the CAT 931 Steering System
The Caterpillar 931 track loader uses a mechanical steering system based on dry clutches and brake bands. Steering is achieved by disengaging the clutch and applying the brake on one side, allowing the opposite track to continue driving and pivoting the machine. Over time, wear in the brake bands, linkage, and clutch components can lead to degraded steering performance—especially uneven braking between left and right sides.
In one case, the left brake required excessive pedal force and became less effective as the machine warmed up. A pulsating growl was heard during braking, and adjustments yielded mixed results. This prompted a deeper look into the brake system’s mechanics and wear points.
Terminology Explained
- Dry Clutch: A friction-based clutch system that operates without hydraulic fluid, relying on mechanical linkage
- Brake Band: A curved friction strip that wraps around a rotating drum to slow or stop motion
- Adjuster Bolt: A threaded bolt used to set brake band tension and clutch engagement
- Clutch Release Bearing: A bearing that allows smooth disengagement of the clutch when the pedal is pressed
Common Symptoms and Observations

• Left brake requires more force than right
  
• Brake effectiveness decreases with heat
  
• Growling or pulsating noise during braking
  
• Limited adjustment range on lower brake bolt
  
• Pressure buildup in final drive housing
  

These symptoms suggest worn brake linings, misadjusted linkage, and possible clutch release wear. The lack of a vent in the final drive housing can also cause pressure buildup, especially during extended operation.
Adjustment Techniques and Their Impact
Two adjustment methods were discussed:
1. Tighten top adjuster bolt, then bottom bolt, back off bottom 1.5 turns, then back off top 3.5 turns
2. Back off both adjusters 1.5 turns after tightening
The first method was initially used, but switching to a 1.5-turn back-off on the top bolt improved braking. This suggests that excessive clearance may have reduced band contact, especially as heat expanded components.
Recommendations:

• Adjust brake bands to achieve minimal clearance without drag
  
• Ensure clutch release linkage has no play before valve engagement
  
• Shorten linkage if pedal travel is excessive
  
• Monitor brake performance after adjustment under load
  

Field Story: Winter Project Planning in Manitoba
A Canadian operator planned to defer full brake replacement until winter, using the machine cautiously in the meantime. After adjusting the linkage and reducing the back-off on the top bolt, the left brake improved but remained weaker than the right. He noted that the bottom adjuster was nearly maxed out, indicating worn linings. The plan was to rebuild the brake system during the off-season.
Additional Parameters and Suggestions

• Brake band material: Asbestos-free woven friction lining
  
• Adjuster bolt thread pitch: ~1.5 mm per turn
  
• Recommended oil for bevel gear case: SAE 30 TDTO
  
• Final drive oil capacity: ~2 gallons per side
  
• Brake pedal force: Should not exceed ~40–50 lbs under normal conditions
  

Preventive Maintenance Tips

• Inspect brake bands and drums every 500 hours
  
• Replace worn linkage bushings and bearings
  
• Use proper oil in clutch compartments to prevent slippage
  
• Vent final drives manually if pressure buildup is noted
  
• Keep adjustment logs for each side to track wear trends
  

Conclusion: Mechanical Steering Requires Mechanical Precision
The CAT 931’s steering system is a testament to mechanical simplicity—but that simplicity demands careful adjustment and regular inspection. Uneven braking, heat sensitivity, and linkage wear can all degrade performance. By understanding the interaction between clutch release, brake band tension, and pedal travel, operators can restore steering responsiveness and plan for long-term repairs. As one technician put it, “If you’re fighting the pedal, the machine’s telling you something—listen before it locks up.”