Champion 720A Axle Nut Service and Rear End Maintenance

[MikePhua]

The Champion 720A and Its Mechanical Legacy
The Champion 720A motor grader was introduced in the mid-1980s as part of Champion Road Machinery’s push to deliver rugged, operator-friendly graders for municipal and contractor use. Built in Goderich, Ontario, Champion machines were known for their mechanical simplicity, robust frames, and ease of service. The 720A featured a Cummins or Detroit Diesel engine depending on configuration, a direct-drive transmission, and a solid rear axle assembly designed for long service life under demanding conditions.
Champion, founded in 1875, had a long history of building graders and road maintenance equipment. Before being acquired by Volvo in the late 1990s, Champion sold thousands of units across North America, with the 720A becoming a staple in rural road departments and small grading contractors.
Axle Nut Function and Assembly Layout
The rear axle nut on the Champion 720A plays a critical role in securing the wheel hub and maintaining preload on the bearings. It is typically a large castellated nut or spanner-style nut threaded onto the axle shaft, backed by a washer and cotter pin or locking tab to prevent rotation.
Key components include:

• Axle shaft
  
• Inner and outer wheel bearings
  
• Hub assembly
  
• Axle nut and washer
  
• Locking mechanism (cotter pin, tab washer, or lock ring)
  

Terminology notes:

• Preload: The axial force applied to bearings during assembly to eliminate play and ensure proper load distribution.
  
• Castellated nut: A nut with notches cut into the outer edge to accept a cotter pin for locking.
  

In Alberta, a grader operator noticed excessive wheel play on his 720A. Upon inspection, the axle nut had backed off slightly due to a worn cotter pin, allowing the hub to shift and accelerate bearing wear.
Disassembly and Inspection Procedure
Servicing the axle nut requires careful disassembly and cleanliness. Suggested steps:

• Block the machine and remove the rear wheel
  
• Drain axle oil if necessary
  
• Remove hub cap and inspect for metal debris
  
• Extract cotter pin or lock tab
  
• Use a spanner wrench or socket to remove the axle nut
  
• Slide off the hub and inspect bearings, races, and seals
  

Inspection tips:

• Check bearing rollers for pitting or discoloration
  
• Inspect races for scoring or uneven wear
  
• Examine the axle threads and nut for damage
  
• Clean all components with solvent and lint-free cloths
  
• Replace seals and gaskets during reassembly
  

In Tennessee, a grading crew rebuilt their rear hub after discovering water intrusion. The bearings were rusted, and the seal lip had torn. After replacing all components and repacking with high-temp grease, the hub ran smoothly under load.
Torque Specifications and Reassembly Strategy
Proper torque and bearing preload are essential for long-term reliability. While exact specs may vary by axle model, a typical procedure involves:

• Torque the axle nut to 200–300 ft-lbs while rotating the hub
  
• Back off the nut slightly (e.g., 1/4 turn) to relieve excess preload
  
• Re-torque to a lower value (e.g., 50–75 ft-lbs) for final setting
  
• Install cotter pin or locking tab aligned with nut slots
  
• Refill axle housing with gear oil if drained
  
• Reinstall wheel and torque lug nuts to spec
  

Suggested upgrades:

• Use a torque multiplier for large nuts
  
• Replace cotter pins with new stainless steel versions
  
• Apply anti-seize to threads for easier future service
  
• Add a magnetic plug to the hub cap to catch debris
  

In South Africa, a vineyard crew added a temperature sensor to their rear hub. This helped monitor bearing health during long grading runs and prevented overheating.
Preventive Maintenance and Long-Term Reliability
To extend axle life and prevent nut-related failures:

• Inspect axle nuts and hub play every 500 hours
  
• Replace seals and repack bearings annually
  
• Monitor oil level and condition in axle housing
  
• Check for vibration or noise during travel
  
• Log service intervals and bearing replacements
  

Suggested spares to stock:

• Axle nuts and washers
  
• Cotter pins or locking tabs
  
• Bearing sets and races
  
• Hub seals and gaskets
  
• High-temp grease and gear oil
  

In New Zealand, a contractor added hub inspections to his pre-shift checklist. This helped catch early signs of bearing wear and prevented roadside breakdowns during rural grading contracts.
Operator Stories and Field Wisdom
In Florida, a demolition crew rebuilt their 720A rear axle after noticing oil seepage and hub heat. The axle nut had loosened due to a missing lock tab. After installing a new nut and tab washer, the machine returned to full service.
In Poland, a snow-clearing team used their 720A for winter road maintenance. After upgrading to sealed bearings and synthetic gear oil, they reduced service intervals and improved cold-weather performance.
Conclusion
The axle nut on a Champion 720A may seem like a small part, but it anchors the integrity of the entire rear hub assembly. With proper torque, clean installation, and regular inspection, this component ensures safe travel, smooth grading, and long bearing life. Whether shaping gravel or clearing snow, keeping the axle nut tight and the hub healthy is a small task with big consequences.