Komatsu 6127-31-1012 crankshaft replacement for D155A bulldozers with S6D155 15.2L engines. Forged alloy steel resists wear. Fleet supply and export ready
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Heavy-duty forged alloy steel crankshaft for Komatsu S6D155 and SA6D155 engines.
Induction hardened journals prevent heavy load bearing scuffing under extreme earthmoving stress.
OEM: 6127-31-1012 | Cross-reference: 6127-31-1011, 6127-31-1114. Fits Komatsu D155A bulldozers and WA600 loaders.
Fleet supply and export ready.
The Komatsu S6D155 and SA6D155 engine series represents a massive 15.2L inline-6 heavy-duty diesel platform (15,240 cc) engineered specifically to drive heavy machinery, including Komatsu D155A-1, D155A-2, and D155A-3 bulldozers, WA600 loaders, and PC600 excavators operating in grueling mining and quarrying environments. At the rotational center of this high-torque powertrain is the premium Komatsu S6D155 crankshaft (OEM 6127-31-1012, cross-reference 6127-31-1011, 6127-31-1114, 6127311012), which converts linear piston forces into continuous driving torque. To maintain peak combustion efficiency and prevent exhaust black smoke under severe earthmoving cycles, this core component of Komatsu S6D155 engine parts (OEM 6127-31-1012) relies on the high-performance induction hardened journal treatment. While lighter applications can utilize cast shafts, our forged steel crankshaft S6D155 assembly is precision-manufactured from high-tensile forged alloy steel to ensure maximum wear resistance under continuous torsional loads. In severe, high-vibration heavy-duty shifts, common failure modes include bearing oil-film shear, causing heavy load bearing scuffing damage or progressive main journal fatigue cracking along the journal fillet shoulders. To counter these stresses, each forged steel crankshaft S6D155 features induction-hardened main journals (125mm standard) and rod pins (102mm standard) finished with strict roundness limits. Rebuilders must check the crankshaft thrust play (standard: 0.050 to 0.220 mm) and verify the bearing oil clearance (standard: 0.050 to 0.096 mm) during any major 6127-31-1012 crankshaft replacement overhaul. This meticulous engineering makes it the ultimate Komatsu bulldozer crankshaft and Komatsu D155A dozer crankshaft replacement option, ensuring long-term rotation reliability for global mining fleets.
| Parameter | Value |
|---|---|
| Engine Code | Komatsu S6D155 / SA6D155 / SA6D155-4 (15.24L) |
| Configuration | Inline-6 Cylinders, 12 Valves OHV |
| Engine Cylinder Bore | 155.0 mm |
| Crankshaft Stroke | 170.00 mm (6.6929 in) |
| Bare Crankshaft Length | 1658.00 mm (65.275 in) |
| Main Journal Diameter | 125.00 mm (Standard Range: 124.95 – 125.00 mm) |
| Rod Pin Diameter | 102.00 mm (Standard Range: 101.95 – 102.00 mm) |
| Crankshaft Net Weight | 243.50 kg (536.8 lbs) |
| Material Spec | Precision Forged Alloy Steel (42CrMo equivalent) |
| Hardness Treatment | Induction Hardened Journals (HRC 52-58) |
| Primary OEM Number | 6127-31-1012 |
| Interchange References | 6127-31-1011, 6127-31-1114, 6127311012 |
Our Komatsu engine components catalog covers the full light-duty and heavy-duty inline families, from the 2.8L 4D94E and 3.3L S4D95 to the massive 11.0L SAA6D125 and 15.2L S6D155 lines. Explore our complete range of Komatsu diesel engine parts by visiting our Komatsu Brand Hub to find matching cylinder heads, cylinder liners, and camshaft assemblies.
| Engine Model | Primary Part Number | Machine Model |
|---|---|---|
| S4D95 | 6204-33-1100 | PC60-5 WA150 Loader |
| S4D102 | 6732-31-1100 | PC120-6 PC100-6 Excavator |
| S6D95 | 6207-31-1100 | PC200-5 PC200-6 Excavator |
| S6D102 | 6735-01-1310 | PC200-6 PC200-7 Excavator |
| S6D105 | 6136-31-1110 | PC200-3 Excavator |
| S6D107 | 6754-01-1310 | PC200-8 Excavator |
| S6D108 | 6222-31-1110 | PC300-6 Excavator |
| S6D110 | 6138-31-1110 | PC220-5 GD605 Grader |
| S6D114 | 6742-01-1570 | PC300-7 PC300-8 Excavator |
| S6D125 | 6151-31-1110 | PC400-3 PC400-5 Excavator |
| S6D140-2 | 6211-31-1010 | PC600-6 Excavator |
| S6D140-3 | 6217-31-1010 | PC750-6 PC800 Excavator |
| S6D140-5 | 6261-31-1200 | PC800-8 PC850-8 Excavator |
| S6D155 | 6127-31-1012 | D155A-2 Bulldozer |
| NT855 | 6710-31-1111 | D85 Bulldozer |
| NH220 | 6623-31-1111 | D60 Bulldozer |
| S6D170 | 6245-31-1100 | PC1250-7 Excavator |
| 4D95L | 6204-31-1201 | PC60 PC75 Excavator |
| 4D94E/4TNE94 | - | PC30 PC35 PC40 Excavator |
Komatsu crankshafts fit heavy machinery including Komatsu D155A Bulldozer, Komatsu WA600 Wheel Loader, Komatsu PC600 Excavator, and Komatsu D150A-1 Bulldozer.
Contact us for complete application coverage.
| Make | Machine / Vehicle Model | Year Range | Engine Code | Crankshaft OEM |
|---|---|---|---|---|
| Komatsu | D155A-1 / D155A-2 Crawler Bulldozer (D155A crankshaft) | 1982–1998 | S6D155-4 | 6127-31-1012 |
| Komatsu | D155A-3 Mining Bulldozer (D155A-2 crankshaft) | 1995–2003 | SA6D155-4 | 6127-31-1012 |
| Komatsu | WA600-1 Heavy Wheel Loader | 1985–1996 | SA6D155-4 | 6127-31-1012 |
| Komatsu | PC600-1 / PC650-1 Heavy Excavator (PC600 crankshaft) | 1988–1997 | S6D155-4 | 6127-31-1012 |
Symptom: Metallic knocking sounds from the lower block, low engine oil pressure when warm, and rough idling during early startup. (heavy load bearing scuffing)
Diagnosis: Oil contamination or low oil pressure degrades the lubricating film on the journal bearing. This causes direct metal-to-metal contact, leading to rapid journal bearing wear, excessive shaft play, and eventual housing contact.
Solution: Replace the crankshaft with a precision-balanced unit, use high-grade filters, and replace the engine oil pump and oil supply lines during overhaul.
Symptom: Hairline cracks on fillet radiuses, crankshaft snapping, or complete engine seizure under severe loading shifts. (S6D155 forging)
Diagnosis: Standard cast iron crankshafts have a random grain structure and lower tensile strength, making them susceptible to stress-fatigue cracking under high-torque digging cycles.
Solution: Sourcing an OEM-spec S6D155 forging (6127-31-1012) ensures a highly aligned grain structure with superior torsional and fatigue strength, safely enduring continuous high-idle excavator operations.
Symptom: Mismatched clearances, rapid bearing wear, or thrust washer binding shortly after initial engine startup. (6127-31-1012 crankshaft replacement)
Diagnosis: Incorrect torque sequence or improper bearing tolerances stretch main bolts unevenly, creating uneven oil clearances and leading to bearing failure.
Solution: Torque the main bearing cap bolts starting from the center cap outward in three progressive stages to the final specification of 285 to 304 Nm (210 to 224 lbf·ft) using clean engine oil. Use Plastigage to confirm standard oil clearance (0.050 to 0.096 mm).
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