Diagnosing Hydraulic Cylinder Removal and Hub Noise on the CAT 426B

[MikePhua]

The CAT 426B and Its Role in Backhoe Evolution
The Caterpillar 426B is a mid-1990s backhoe loader that helped define the transition from purely mechanical systems to more integrated hydraulic platforms. Produced by Caterpillar Inc., a company founded in 1925 and now one of the world’s largest construction equipment manufacturers, the 426B was part of a lineage that emphasized durability, operator comfort, and serviceability. With a Perkins 4-cylinder diesel engine producing around 85 horsepower and a robust hydraulic system, the 426B was widely adopted across North America for utility work, road maintenance, and small-scale excavation.
By the late 1990s, Caterpillar had sold tens of thousands of backhoe loaders globally, with the 426B contributing significantly to its market share. Its reputation for reliability made it a staple in municipal fleets and private contracting outfits.
Removing the Bucket Hydraulic Cylinder Safely
Removing the bucket cylinder on a CAT 426B requires careful planning due to its weight and hydraulic complexity. A minor seal breach—such as a piece of bark wedged under the gland nut—can cause a slow hydraulic weep. While not immediately catastrophic, such leaks can worsen in cold weather and compromise system pressure.
Recommended removal procedure:

• Extend the backhoe onto the ground and curl the bucket slightly inward to create slack
  
• If available, use a crane or service truck with a sling to support the cylinder behind the head end and ahead of the hydraulic fitting
  
• Remove the snap ring securing the rod-end mounting pin and extract the pin
  
• If no crane is available, use a wooden block to support the cylinder without stressing the 90-degree fitting
  
• Start the machine and retract the cylinder rod fully, then shut off the engine
  
• Turn the key to the “on” position and cycle all backhoe controls to relieve residual hydraulic pressure
  
• Disconnect the two hydraulic lines (typically -8 and -10 sizes, requiring 15/16" and 1-1/8" wrenches) and cap them
  
• Remove the snap ring and head-end mounting pin to free the cylinder
  

The cylinder weighs over 100 lbs and will shift when disconnected, so mechanical support is essential. After repair, reinstall in reverse order, ensuring all seals are properly seated and hydraulic lines are torqued to spec.
Ticking Noise in the Front Left Hub
A separate issue often reported on the 426B is a clicking or ticking sound from the front left hub during low-speed turns, regardless of whether the machine is in 2WD or 4WD. This symptom typically points to wear in the final drive assembly, wheel bearings, or spindle components.
Diagnostic steps:

• Drain the final drive oil into a clean container and inspect for metal shavings or debris
  
• Rotate the hub to the 3 o’clock position for optimal drainage and refill with manufacturer-specified oil (usually less than 1 liter)
  
• Check for play in the wheel bearing by rocking the wheel laterally
  
• Inspect the spindle for scoring or pitting
  
• Examine the CV joint boots for cracks or grease leakage
  

In one case from Ontario, a contractor discovered that the ticking sound was caused by a partially fractured bearing race. The damage was only visible after disassembly, and the bearing had been generating harmonic noise under load. Replacing the bearing and flushing the hub resolved the issue.
Hydraulic System Considerations in Cold Weather
Cold temperatures exacerbate minor hydraulic leaks and can stiffen seals, leading to increased wear. The CAT 426B’s open-center hydraulic system relies on consistent fluid viscosity and pressure regulation. During winter, operators should:

• Use low-temperature hydraulic fluid rated for the operating climate
  
• Warm up the machine for at least 10 minutes before engaging heavy functions
  
• Inspect gland nuts and cylinder seals for signs of hardening or shrinkage
  
• Keep hydraulic lines clean and capped during service to prevent contamination
  

In Vermont, a fleet manager reported that switching to synthetic hydraulic fluid reduced seal failures by 40% during winter months.
Preventive Maintenance and Long-Term Reliability
To extend the life of the CAT 426B and prevent recurring issues:

• Perform monthly inspections of all hydraulic cylinders for weeping or scoring
  
• Replace worn snap rings and mounting pins with OEM-grade components
  
• Flush final drive oil annually and inspect for contamination
  
• Keep a log of noises or performance changes to aid in early diagnosis
  
• Train operators to recognize early signs of hydraulic fatigue and hub wear
  

In Texas, a utility company implemented a quarterly maintenance checklist that included cylinder seal inspections and hub oil sampling. Over two years, they reduced unscheduled downtime by 60%.
Conclusion
The CAT 426B remains a dependable workhorse decades after its release, but like all aging machines, it demands attentive maintenance. Whether dealing with a minor hydraulic leak or diagnosing hub noise, a methodical approach rooted in mechanical understanding and field experience ensures safe and effective repairs. With proper care, the 426B continues to serve as a testament to Caterpillar’s legacy of rugged, field-ready engineering.