Swapping a Komatsu D31P-16 Engine into a D31P-17 Chassis

[MikePhua]

The Komatsu D31P Series and Its Evolution
The Komatsu D31P series dozers have long been favored for their compact footprint, low ground pressure, and reliability in soft terrain. The D31P-16, introduced in the late 1980s, featured a 4-cylinder Komatsu diesel engine, hydrostatic transmission, and a fully enclosed operator station. It was widely used in forestry, grading, and utility work. The D31P-17, which followed in the early 1990s, retained much of the mechanical DNA of its predecessor but introduced refinements in steering clutch design, undercarriage durability, and operator ergonomics.
Komatsu Ltd., founded in 1921 in Japan, has produced millions of machines globally. The D31 series alone has seen tens of thousands of units sold across North America, Southeast Asia, and Europe. The -16 and -17 variants share many components, making them attractive candidates for part interchange and restoration.
Terminology Annotation
- Chassis: The structural frame of the dozer, including the undercarriage, transmission, and mounting points.
- Running Gear: The complete set of undercarriage components—tracks, rollers, idlers, and sprockets.
- Steering Clutch: A mechanical assembly that allows differential steering by disengaging drive to one track.
- Engine Swap: The process of removing an engine from one machine and installing it into another, often requiring adaptation of mounts, wiring, and controls.
- Hydrostatic Drive: A transmission system using hydraulic fluid to transfer power from the engine to the tracks.
Assessing the Feasibility of the Swap
Swapping the engine from a D31P-16 into a D31P-17 is mechanically feasible, but not without caveats. Both machines use similar engine blocks and mounting patterns, but differences in wiring harnesses, control linkages, and hydraulic routing must be addressed. The -17 series often includes updated steering clutch actuation and slightly revised hydraulic pump configurations.
Before proceeding, technicians should:

• Compare engine mount dimensions and bolt patterns
  
• Inspect bell housing compatibility and transmission input shaft alignment
  
• Verify throttle linkage geometry and governor control
  
• Examine hydraulic pump couplings and pressure ratings
  
• Check electrical connectors for monitor panel integration
  

In one documented case, a D31P-16 engine was successfully installed into a -17 chassis after minor modifications to the throttle cable bracket and fuel line routing. The swap restored a machine that had recently received new tracks, clutches, and rollers—making the effort worthwhile.
Why the Chassis Condition Matters
The decision to swap engines often hinges on the condition of the chassis. In this scenario, the D31P-16 had a functioning engine but a deteriorated frame, while the D31P-17 had a failed engine but a recently rebuilt undercarriage. Investing in the -17 chassis makes sense, especially when steering clutches and running gear have already been replaced—components that can cost upwards of $8,000 when sourced new.
A contractor in Minnesota shared that his D31P-17 had undergone a full undercarriage rebuild just months before the engine seized. Rather than scrapping the machine, he sourced a donor engine from a -16 and completed the swap over a weekend with two mechanics and a forklift. The machine returned to service the following Monday.
Potential Pitfalls and Solutions
Common challenges during such swaps include:

• Mismatched flywheel housings requiring adapter plates
  
• Incompatible starter motor wiring
  
• Differences in cooling system hose routing
  
• Exhaust manifold clearance issues with the hood or firewall
  

Solutions include:

• Fabricating custom brackets or spacers
  
• Reusing the original starter and alternator from the target machine
  
• Installing flexible coolant hoses with reinforced clamps
  
• Modifying exhaust routing with heat shielding and support hangers
  

Technicians should also inspect the donor engine for signs of long-term storage damage, such as stuck injectors, dry seals, or rust in the cylinder liners. A compression test and oil analysis are recommended before installation.
Maintenance Strategy Post-Swap
After completing the swap:

• Change all fluids—engine oil, coolant, hydraulic fluid
  
• Replace fuel filters and bleed the system
  
• Inspect and adjust throttle and governor linkages
  
• Monitor engine temperature and oil pressure during first 10 hours
  
• Retorque engine mount bolts after initial operation
  

Operators should also document the swap for future service reference, noting any part substitutions or wiring changes. This helps avoid confusion during diagnostics or resale.
Conclusion
Swapping a Komatsu D31P-16 engine into a D31P-17 chassis is a practical solution when one machine has a strong powerplant and the other a solid frame. With careful planning, minor fabrication, and attention to compatibility, the result can be a fully functional dozer ready for years of service. In the world of heavy equipment, resourcefulness often trumps replacement—and breathing new life into old iron is both economical and deeply satisfying.