Replacing Lever Bearings on a CAT 931B Track Loader

[MikePhua]

The CAT 931B and Its Mechanical Legacy
The Caterpillar 931B track loader was introduced in the early 1980s as part of Caterpillar’s push to modernize its small-to-mid-size crawler loader lineup. With an operating weight of approximately 13,000 kg and powered by the reliable Cat 3204 diesel engine, the 931B offered a balance of maneuverability and breakout force that made it popular in construction, agriculture, and municipal work. Caterpillar, founded in 1925, had by then become a global leader in earthmoving equipment, and the 931B contributed to its reputation for building machines that were both durable and field-serviceable.
Sales of the 931B were strong throughout the 1980s and early 1990s, especially in North America and parts of Europe. Its mechanical simplicity—no complex electronics, straightforward hydraulics, and robust steel construction—made it a favorite among independent contractors and fleet managers alike. Today, many units remain in service, especially in rural areas where reliability trumps modern features.
Diagnosing Lever Arm Play and Bearing Wear
One of the most common mechanical issues in aging track loaders like the 931B is excessive play in the loader lever arms. These arms connect the lift and tilt cylinders to the bucket and frame, and their pivot points rely on bushings, bearings, and pins to maintain alignment and absorb stress.
Symptoms of bearing wear include:

• Noticeable lateral movement at the base of the lever arms
  
• Difficulty maintaining bucket angle under load
  
• Audible clunking during lift or tilt operations
  
• Accelerated seal wear due to misalignment
  

In one case, a retired real estate broker turned equipment restorer noticed significant movement in the bottom lever arms of his 931B. Despite having a repair manual, he found no guidance on bearing replacement procedures, prompting a hands-on diagnostic approach.
Disassembly Strategy and Safety Considerations
Removing lever bearings requires careful planning, especially when working without a full-service shop. The loader arms are heavy and under tension, so stabilizing the bucket and using a chain hoist or crane is essential.
Recommended steps:

• Position the bucket flat on the ground to relieve pressure on the linkage
  
• Loosen bolts and pins while the arms are supported
  
• Remove the tilt pin and swing the lever arm outward for access
  
• Use a wedge or mechanical spreader to separate components safely
  
• Avoid removing the top connection unless necessary—partial disassembly can suffice
  

A small chain hoist proved invaluable in one repair, allowing the operator to swing the lever arm forward and access the bearing housing without removing the entire assembly.
Removing Old Bearings and Installing New Components
Old bearings can be stubborn, especially if they’ve seized or worn unevenly. A proven technique involves welding beads inside the bearing race. As the weld cools, it contracts the metal, allowing the bearing to shrink and release from the housing.
Additional tips:

• Heat the bushing with a torch to expand it before removal
  
• Use anti-seize compound on new bearings to ease future service
  
• Press new bearings in with a hydraulic press or threaded puller
  
• Inspect the pins for wear—anything over 1/16" play is excessive
  
• Replace seals in pairs to ensure uniform sealing pressure
  

In one instance, the installer found the pins to be visibly grooved, prompting a full replacement. At roughly $40 per pin, the cost was manageable, and aftermarket suppliers offered competitive pricing compared to OEM dealers.
Addressing Frame Wear and Shim Installation
Beyond bearings and pins, face wear on the lever arm mounting surfaces can contribute to slop in the linkage. Installing shims during reassembly helps restore proper spacing and reduces lateral movement.
Shim installation advice:

• Measure face wear with feeler gauges before assembly
  
• Use hardened steel shims to prevent compression under load
  
• Apply grease between shims and mating surfaces to prevent corrosion
  
• Recheck torque specs after 10 hours of operation to ensure stability
  

A lineborer from Western Australia noted that cumulative wear across multiple pivot points can lead to a loose frame feel, even if individual components seem acceptable. Addressing all wear points simultaneously yields the best results.
Parts Sourcing and Cost Management
For the 931B, parts are still widely available through Caterpillar dealers and aftermarket suppliers. In one documented rebuild:

• 4 lever bearings
  
• 4 seals
  
• 4 new pins
  
• 8 additional seals for auxiliary pivots
  

Total cost: just over $200 from the dealer, with additional components sourced from a third-party supplier at reduced rates. UPS delivery ensured timely installation, and the operator reported that the new parts eliminated all noticeable play in the linkage.
Final Assembly and Field Testing
After installing the new bearings and pins, the lever arms were reassembled and painted. The operator noted that the left side was completed first, followed by the right. With all eight bearings and sixteen seals replaced, the loader bucket regained its original responsiveness.
Field testing confirmed:

• No lateral slop in the lever arms
  
• Smooth bucket tilt and lift under load
  
• No seal leakage after 10 hours of operation
  
• Improved operator confidence and control
  

This kind of restoration not only extends the life of the machine but also improves safety and productivity. In many cases, older machines like the 931B outperform newer models in harsh environments due to their mechanical resilience.
Conclusion
Replacing lever bearings on a CAT 931B is a rewarding task that restores precision and prolongs service life. With careful disassembly, proper tooling, and attention to wear patterns, even a decades-old track loader can be brought back to peak performance. The 931B remains a testament to Caterpillar’s engineering philosophy: build it tough, make it fixable, and keep it working. Whether you're a seasoned mechanic or a weekend restorer, tackling lever arm repairs is a rite of passage in the world of heavy equipment maintenance.