Removing a Chain Link on a Caterpillar D4 Dozer

[MikePhua]

The D4 Series and Undercarriage Wear
The Caterpillar D4 dozer has long been a staple in mid-size earthmoving, forestry, and agricultural work. Introduced in the 1930s and evolving through decades of mechanical refinement, the D4 became known for its balance of power, maneuverability, and serviceability. By the late 1960s, models like the D4C and D4H featured sealed and lubricated track (SALT) systems, hydraulic adjusters, and modular undercarriage components.
Undercarriage wear is inevitable in tracked machines. Track chains stretch, bushings wear, and idlers reach the limits of their adjustment. When the track slack exceeds manufacturer tolerances—typically around 5 inches of sag between the idler and carrier roller—operators must decide whether to replace the chain or attempt a link removal to restore tension.
Why Remove a Link Instead of Replacing the Chain
Removing a link is a field-expedient method to extend the life of a worn track chain. It’s not a factory-recommended solution, but in low-hour machines or remote operations, it can restore functionality without the cost or logistics of full replacement.
Reasons operators choose to remove a link:

• The machine sees minimal use (e.g., 5–10 hours per year)
  
• The idler is fully extended and cannot tension the chain further
  
• The sprockets and rollers are still in good condition
  
• The chain is worn but not structurally compromised
  
• Replacement parts are unavailable or delayed
  

One example involved a D4 used on a farm in Iceland. The machine had slack in the right track, but the idler and sprocket were in excellent shape. Rather than install a new chain, the owner explored link removal to tighten the track.
Track Types and Link Removal Feasibility
Before attempting link removal, it’s critical to identify the track type:

• Standard sealed track: Contains a master pin and can be disassembled with heat and force.
  
• SALT (Sealed and Lubricated Track): More complex, with internal lubrication and press-fit pins. Link removal is difficult and often impractical.
  
• Wet link chains: If lubrication has failed and the chain is dry, link removal may be possible as a last resort.
  

Operators must inspect for a master pin—usually identifiable by a dimple or flush head. If present, the track can be broken at that point. If not, cutting and welding may be required.
Methods for Removing a Link
There are several approaches depending on tooling and track condition:

• Master Pin Removal
  • Locate the master pin and remove the track plate
    
  • Use a torch to burn the ends of the pin
    
  • Drive the pin out with a sledge or press
    
  • Remove the adjacent link and reassemble the chain
    
• Torch and Weld Method
  • Cut two adjacent links between bolt holes
    
  • Trim the ends and bring the chain together
    
  • Bolt on the plate and weld the link to restore continuity
    
  • Only recommended for worn chains with no lubrication
    
• Cut and Rejoin Technique
  

• Cut through the bush and pin of the worn link
  
• Burn out the remaining pin stubs from the adjacent link
  
• Reuse the master pin or fabricate a replacement
  
• Reassemble with spot welds or press-fit pins
  

One technician in the UK reported removing two links from a Komatsu D61 chain using this method, restoring proper adjustment without replacing the chain.
Precautions and Best Practices
Removing a link is not without risks. Improper cuts, misaligned reassembly, or weakened welds can lead to chain failure under load. To minimize risk:

• Use a cutting torch with precision to avoid damaging adjacent links
  
• Clean the area behind the idler before retracting the adjuster
  
• Release grease from the tensioner slowly to avoid hydraulic shock
  
• Use a steel slug or round bar to help retract the idler via sprocket rotation
  
• Apply penetrating oil to rusted components days in advance
  
• Inspect the recoil spring and button bar for binding or missing bolts
  

In one case, an idler appeared fully extended but was actually rusted in place. After applying diesel and working the machine in reverse with a steel slug in the sprocket, the idler moved back, allowing the chain to be rejoined.
Field Anecdotes and Improvised Solutions
A dozer in the Australian outback had both tracks shortened using the weld-and-bolt method. The machine was used for pushing drought feed and saw minimal load. The repair held for years, with the links welded directly to the plates.
Another operator in North Dakota suggested using spot welds to hold the master pin in place after reassembly. While not ideal for high-hour machines, it worked for older tractors with limited use.
Recommendations for Operators
Before removing a link:

• Confirm track type and presence of master pin
  
• Inspect idler travel and recoil spring condition
  
• Evaluate chain wear and structural integrity
  
• Prepare cutting and welding tools
  
• Document the process for future maintenance
  
• Store removed pads and links for later use
  

After reassembly:

• Test track tension and alignment
  
• Monitor for abnormal noise or vibration
  
• Avoid high-speed travel or aggressive turns
  
• Plan for eventual chain replacement
  

Conclusion
Removing a chain link on a Caterpillar D4 is a practical solution for extending track life in low-demand scenarios. While not a substitute for proper undercarriage maintenance, it offers a way to restore tension and functionality when parts are scarce or budgets tight. With careful execution and awareness of track design, operators can perform this task safely and effectively, keeping their machines working until full replacement becomes necessary.