Rebuilding a Komatsu D155AX-6 Dozer with the Right Technical Resources

[MikePhua]

Komatsu’s Legacy and the D155AX-6 Platform
Komatsu, founded in 1921 in Japan, has grown into one of the world’s largest manufacturers of construction and mining equipment. Known for its innovation in crawler dozers, Komatsu introduced the D155 series as a mid-to-large class dozer for heavy-duty earthmoving, mining, and land development. The D155AX-6, part of the Dash-6 generation, features a powerful SAA6D140E-5 engine producing over 350 horsepower, a hydrostatic steering system, and an electronically controlled powertrain. It is widely used in quarrying, forestry, and large-scale grading operations.
Preparing for a Major Rebuild
When preparing to rebuild a Komatsu D155AX-6, the most critical step is acquiring the correct technical documentation. This includes:

• Service manual: Contains disassembly procedures, torque specs, and adjustment tolerances
  
• Parts book: Provides exploded diagrams and part numbers for ordering replacements
  
• Operator’s manual: Offers insights into machine operation and maintenance intervals
  

Without these documents, even experienced technicians risk incorrect torque application, missed wear limits, or improper reassembly. For example, the torque specification for the final drive bearing preload nut differs significantly from earlier D155 models, and using outdated specs can lead to premature failure.
Sources for Manuals and Technical Data
While Komatsu dealers offer printed manuals, they can be expensive—often exceeding $200 USD per volume. However, several alternative sources exist:

• Digital repositories: Some online catalogs offer free access to Komatsu parts books, searchable by model and serial number. These are especially useful for identifying component revisions across production years.
  
• Subscription platforms: Sites like Scribd occasionally host downloadable manuals for specific serial number ranges (e.g., 80001 and up). These may include engine overhaul procedures, hydraulic schematics, and electrical diagrams.
  
• Aftermarket CD-ROMs: Available through auction sites, these discs often include scanned manuals for multiple Komatsu models. While not always up to date, they can be a cost-effective starting point.
  

One technician in New Zealand noted that his local dealer quoted $200 NZD for a printed parts book, but he found a digital version online that covered the same content for free. He used it to identify the correct SAA6D140E-5 engine configuration and order gaskets and bearings for a top-end rebuild.
Key Considerations During Rebuild
When rebuilding a D155AX-6, attention should be paid to:

• Engine internals: Verify liner protrusion, piston ring end gap, and valve lash settings
  
• Transmission calibration: Use diagnostic software to reset clutch pack pressures and shift timing
  
• Hydraulic system flushing: Contaminants from failed components can damage new parts
  
• Undercarriage inspection: Rebuilds often coincide with track frame and roller replacement
  

Torque specs for major components such as cylinder head bolts, main bearings, and final drive assemblies must be followed precisely. For example, the cylinder head bolts on the SAA6D140E-5 require a multi-step torque-and-angle sequence, and skipping steps can lead to head gasket failure.
Recommendations for Smooth Execution

• Begin with a serial number-specific manual to ensure compatibility
  
• Use OEM or high-quality aftermarket parts for critical components
  
• Document all torque values and clearances during disassembly
  
• Replace all seals, gaskets, and wear rings during reassembly
  
• Perform a full systems test before returning the machine to service
  

Conclusion
Rebuilding a Komatsu D155AX-6 is a complex but rewarding task that demands precision, planning, and the right documentation. With access to accurate manuals and a methodical approach, operators and technicians can restore these powerful machines to peak performance. The D155AX-6 remains a cornerstone of Komatsu’s dozer lineup, and with proper care, it can continue to deliver decades of reliable service.