Cat 931B Brake Parts

[MikePhua]

The Caterpillar 931B is a track‑type loader introduced as the successor to the original 931 in the late 1970s, featuring improvements such as stronger breakout force and modified brake systems over its predecessor. These machines were built in large numbers during the 1980s and remain popular with collectors and operators of legacy Caterpillar equipment due to their robust construction and mechanical simplicity. One common maintenance area for older 931B machines is the brake system, which plays a crucial role in both stopping the loader and assisting in steering through controlled differential action. Understanding the components of the brake system, common wear points, and maintenance considerations helps operators keep these classic machines safe and functional.
Brake System Terminology and Basics
To understand brake parts on a 931B, it helps to know a few key terms:

• Brake Band – A steel band lined with friction material that wraps around a drum to slow or hold motion. Many older Caterpillar track loaders use dry brake bands rather than wet multi‑disk units, meaning the bands operate without oil immersion.
  
• Brake Drum/Brake Housing – The surface around which the brake band tightens; it rotates with the drivetrain or transmission component.
  
• Adjustment Rod/Linkage – The mechanical linkage that sets the brake band tension to ensure proper engagement. Incorrect adjustment can cause weak or inconsistent braking.
  
• Friction Material (Brake Lining) – The replaceable surface bonded or riveted to the brake band that provides resistance against the drum. Lining thickness affects braking force and lifespan.
  
• Brake Actuator/Wheel Cylinder – In systems with hydraulics, cylinders push the brake bands or shoes into contact; on dry systems this may be a mechanical actuation instead.
  

On the 931B, the brake bands are typically dry‑type mechanical bands controlling transmission or planetary motion during steering and stopping. These older brake bands differ from modern oil‑cooled multi‑disk systems found on newer machines, and they require periodic adjustment and lining replacement as part of regular maintenance.
Core Brake Components Found on 931B Loaders
Brake parts for the Cat 931B can be grouped into several categories:

• Brake Bands and Lining
  • Bands with riveted or bonded friction material
    
  • Adjustment hardware and clips
    
• Brake Drums/Housings
  • The rotating surface the band contacts
    
• Adjustment Linkage
  • Rods and nuts that set brake tension
    
  • Return springs and retaining hardware
    
• Brake‑Related Friction Discs
  • Some loaders share disc friction parts used in steering clutches or brakes in more complex assemblies.
    
• Associated Hardware
  • Pins, clips, springs, and fasteners that hold bands and linkage in place
    

These parts are available in new OEM, aftermarket, or used condition, and sourcing them through parts catalogs helps ensure correct fitment for the machine’s serial prefix and configuration.
Brake Adjustment and Wear Considerations
Brake band systems on older tracked machines like the 931B require regular attention:

• Wear of friction lining – Over time, the lining on the brake bands wears thinner, reducing braking effectiveness. A typical lining thickness when new might be several millimeters; worn bands may need replacement before uneven wear leads to slippage.
  
• Adjustment rod condition – The rods that set band tension can strip or wear, leading to inconsistent brake application. Replacement of worn adjustment hardware often restores performance.
  
• Dry brake behavior – Dry systems can feel “funny” or inconsistent compared to modern wet brakes; operators may notice differences between forward and reverse braking, and cold vs. warm performance.
  
• Access and serviceability – Brake bands on the 931B are often located behind covers near the transmission and battery area; gaining access typically requires removing guards or panels prior to inspection or replacement.
  

Unlike wet brakes that run in oil and self‑cool/clean to a degree, dry brake bands accumulate dust and require cleaning or relining more frequently, particularly on machines used in dusty construction environments.
Maintenance Tips and Best Practices
To keep the 931B braking safely and effectively:

• Regular inspection – Check band lining thickness at intervals aligned with operating hours (e.g., every 250–500 hours depending on usage).
  
• Correct adjustment – Use the proper shop manual specifications for brake band tension to ensure even engagement and minimize drag or slippage.
  
• Replace lining and clips together – When replacing brake bands, also replace rivets, clips, and adjustment hardware to ensure longevity and proper function.
  
• Clean before measure – Before measuring wear or adjusting, clean accumulated dust and debris from the brake housing to improve assessment accuracy.
  
• Service manuals as reference – Factory service manuals for the 931B contain diagrams and torque specs that are invaluable when servicing brake parts.
  

These practices help maintain stopping power and reduce the chances of uneven braking or steering issues on tracked loaders.
Real‑World Insights and Anecdotes
Many 931B owners report that left and right brake performance can feel asymmetric due to wear or slack in linkage, which often improves after adjustment or relining of the bands. One operator noted that after an engine and transmission overhaul, uneven braking persisted until the linkage was shortened slightly, improving brake engagement balance.
In another case, a brake specialist pointed out that taking brake bands to an independent brake shop for relining can save money compared to dealer prices and allows reuse of existing hardware when in good condition. Ordering liner material and having it professionally applied often results in a better fit and longer service life than simple pad replacement alone.
Safety and Performance Considerations
Because braking systems directly influence operator safety, servicing them should always be done carefully:

• Use proper blocking and supports when removing heavy brake components.
  
• Check adjustment after relining to ensure bands are not too tight, which can cause drag and overheating, or too loose, which reduces braking force.
  
• Record brake service in machine maintenance logs to track wear patterns and anticipate future needs.
  

Brake systems on old machines like the 931B are mechanical rather than electronic; this means visual inspection and measurement are essential tools in ensuring continued safe operation.
Conclusion
Brake parts on the Caterpillar 931B track loader encompass more than just the friction bands—they include drums, linkage, clips, and related hardware that work together to stop and help steer the machine. Due to its age and dry brake design, routine inspection, correct adjustment, and lining maintenance are key to preserving braking performance. Availability of parts in both new and used conditions helps owners maintain these classic machines, and proper maintenance practices extend service life while improving safety and operational confidence.