D155 Model Overview
The D155 is Komatsu's largest conventional crawler dozer in its standard lineup, positioned above the D85 and below the D275. Three generations cover the bulk of India's working fleet:
- D155A-5: Komatsu SA6D140E-3 engine (pre-Tier), 228 kW (306 hp) — common in 2000s-era mining fleets
- D155A-6: Komatsu SAA6D140E-3, 228 kW, Tier 2 — widespread in Indian coal and iron ore mines
- D155A-7: Komatsu SAA6D140E-5, 228 kW, Tier 4 Final with EGR and DPF — newer units introduced post-2015
Blade variants are SX (semi-U), S (straight), and A (angle). Operating weight is approximately 36 tonnes. Ground pressure is 0.082 MPa with standard triple-grouser shoes.
SAA6D140 Engine — Key Service Parts
The SA6D140 and SAA6D140 share a common block architecture. Most engine consumables are interchangeable across the D155A-5, A-6, and A-7 — and also cross-reference with the GD825-2 motor grader. Confirm part numbers against your serial number prefix before ordering.
| Component | Part Number | Service Interval | Notes |
|---|---|---|---|
| Engine oil filter | 600-211-1231 | 250 hr | Cross-references GD825-2 and D155A-5/6/7 |
| Fuel filter (primary) | 600-319-3750 | 500 hr | Replace together with secondary |
| Fuel filter (secondary) | 6754-79-6140 | 500 hr | Always replace as a pair |
| Air filter (outer) | 6003-18-2520 | 500 hr or restriction indicator | Pre-cleaner strongly recommended on dusty sites |
| Air filter (inner/safety) | 6003-18-2530 | 1,500 hr | Replace only — do not clean or blow out |
| Water pump assembly | 6212-61-1300 | Inspect at 4,000 hr | Weep hole seepage = replace immediately |
| Thermostat | 600-421-1500 | 2,000 hr | Opens 76.5°C; fully open at 91°C |
| Fuel injection pump (HD0-03) | 6212-71-1130 | Overhaul at 10,000 hr | Reman units available — exchange program |
| Piston + rings (per cylinder, 6 cyl) | 6212-31-2100 | At overhaul | Check liner bore before ordering |
| Cylinder liner | 6212-21-2110 | At overhaul if >0.30 mm taper | Measure at TDC, mid-stroke, BDC |
Note: D155A-7 with SAA6D140E-5 uses an EGR system. Inspect EGR cooler for coolant leakage at every 2,000 hr service — a failed EGR cooler on the A-7 will contaminate the intake manifold and result in a costly rebuild.
Final Drive System
The D155A uses two planetary final drives — one per track side. Final drive oil capacity is 17.5 L per side; use SAE 90 gear oil meeting GL-5 specification.
Oil change intervals: first change at 250 hr, then every 1,000 hr thereafter. Common failure modes are sun gear spline wear (part 154-27-11210) and planet gear bearing seizure from oil contamination.
Inspection tip: Pull and inspect the magnetic drain plug at every oil change. A thick metallic paste on the magnet — not just fine black particles — signals imminent planetary failure. Do not defer this check.
Undercarriage Components
Track shoe width is 560 mm (standard triple-grouser for hard ground) or 710 mm wide-shoe for soft ground. Track pitch is 216 mm. Track gauge is 2,130 mm.
| Component | Part Number | Notes |
|---|---|---|
| Track shoe assembly (single, LH=RH) | 155-32-00073 | Replace full set when worn — mixing new/old shoes accelerates link wear |
| Track link assembly (one side) | 154-32-41105 | Always replace in matched left-right sets |
| Carrier roller | 154-30-00088 | Inspect for oil seal leaks at every 500 hr |
| Bottom roller (track roller) | 154-30-00340 | 8 per side; replace when flange worn >5 mm |
| Sprocket (drive tumbler) | 154-27-42520 | Replace together with new track — worn sprocket will destroy new chain in <500 hr |
| Front idler assembly | 154-30-00300 | Includes grease cylinder recoil assembly — service as complete unit |
Measure track sag every 250 hr. Correct sag for D155A is 10–30 mm measured at the center of the upper strand. Over-tensioning in rocky conditions causes accelerated bushing and pin wear.
Blade Cylinder Seals
The straight-blade (S-blade) configuration uses two tilt cylinders and two lift cylinders. Cylinder bore is 150 mm (lift) and 125 mm (tilt). The blade lift cylinder seal kit 707-98-09550 fits D155A-5, A-6, and A-7.
Signs of blade cylinder seal failure: blade drops under load even with implement lock engaged, uneven cutting edge pressure across the width, and visible hydraulic oil weeping from the rod gland. Weeping from the gland wiper seal does not always trigger a fault code — inspect visually at each service.
Caution: When replacing blade cylinder seals, always check the rod surface for scoring or pitting. A scored rod will destroy new seals within hours. Rod surface hardness spec is 54–62 HRC — repair by chrome re-plating if below spec.
India-Specific Operating Notes
Indian coal mine D155s typically run 14–16 hours per day at near-100% load factor. Reduce engine oil change to 150 hr intervals (not the standard 250 hr) when operating in this regime. Final drive oil contamination is the leading cause of catastrophic gearbox failure in these conditions — check for water ingress at every oil change.
Quarry operations on basalt and granite cause accelerated track shoe and bushing wear. Check shoe thickness and bushing OD every 500 hr. In Indian iron ore operations, fine silica dust drastically shortens air filter life — fit a pre-cleaner and inspect the primary element every 100 hr rather than 500 hr.
Procurement tip: Keep minimum stock of one set of final drive seal kits (both sides), one set of air filters (inner + outer), and one blade lift cylinder seal kit on-site for every two D155 units in your fleet. Downtime for these components typically exceeds parts lead time at remote mine sites.
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