Caterpillar D300D
Maintenance schedule, common problems & OEM parts breakdown
The Caterpillar D300D is a 6x6 articulated dump truck built for off-road hauling in mining, quarry, and heavy earthmoving work. It runs a Caterpillar 3306 DITA diesel - turbocharged, aftercooled, direct-injection, and fully mechanically governed with no electronic control module. Gross output is documented between roughly 194 and 213 kW (260-285 hp), a range that reflects different source ratings rather than a running production change. Operating weight sits around 20.7 tonnes (45,600 lb) empty, with a rated payload near 27.2 tonnes (about 59,900-60,000 lb). Caterpillar built the D300D from 1989 to 1995 under the 5MG serial prefix, positioned between the earlier D300B and the 1996-model D300E that replaced it (itself later followed by the D300E II). The truck was offered as a standard flat-floor dump body on Caterpillar's D300-family chassis, sharing its articulated-hitch, powershift-transmission driveline layout with the rest of the D-series line.
The D300 line traces back to DJB Engineering's articulated-truck designs, which Caterpillar began supplying components for in the mid-1980s before absorbing the company into Cat-branded production by the mid-1990s. Across the B-through-D generations Caterpillar kept the 3306 engine family in place while updating fuel-system calibration and power ratings, which is why published gross-power figures for these trucks vary by document and by year rather than marking a real design split. What sets the D300D apart in the used and parts market today is its fully mechanical fuel system: no ECM, no digital fault codes, and little electronics to fail on a machine already decades old. That simplicity keeps diagnostics and rebuild costs predictable, and because the 3306 saw duty across a wide range of Caterpillar machines, engine, transmission, and axle components remain easier to source than on a one-off design. Surviving D300D units today mostly serve as parts donors or budget haul trucks for buyers who value mechanical simplicity over the electronics of later articulated-truck generations.
Below: full specifications, fluids & capacities, the factory service schedule, common service parts, verified fault codes, what owners discuss, attachment guidance, the complete assembly directory, and a serial-number reference. Complete parts lists with full OEM part numbers, exploded diagrams, quantities, and fitment data are available free in Heavy Parts AI.
Caterpillar D300D specifications
Engine
| Engine model | Caterpillar 3306 inline-6 diesel (dealer and used-equipment listings for this model reference the 3306B and 3306 DITA turbocharged-aftercooled variants) |
| Gross power | Reported figures vary by source: 194 kW (260 hp) per some equipment spec databases vs. 212.5 kW (285 hp) per others — varies by source/rating standard, confirm against the engine data plate |
| Displacement | 10.5 L (638 cu in) |
| Cylinders | 6, inline |
| Emissions tier | Built 1989-1995, ahead of EPA and EU nonroad emissions tier rules; mechanically governed diesel with no exhaust aftertreatment |
Weights
| Operating (empty) weight | About 20.7 t (45,600 lb); a lower ~19.8 t figure sometimes cited for this model line belongs to the earlier D300B, not the D300D. |
| Rated payload | About 27.2-27.3 t (roughly 59,966 lb), consistent across equipment spec databases |
| Dump body capacity (heaped) | About 18 m3, per equipment spec databases |
| Ground pressure | Not published in available spec sources for this model |
Dimensions
| Overall length | 9.87 m (32.39 ft) |
| Overall width | 2.88 m (9.45 ft) |
| Overall height | 3.28 m (10.77 ft) |
| Dump (tip) height | 6.42 m (21.07 ft) |
| Tire size | 26.5-25, per equipment spec databases |
| Wheelbase / ground clearance | Not published in available spec sources for this vintage model — check the operation and maintenance manual for exact figures |
Performance
| Dump angle | 55 degrees |
| Travel speed | Not published in available spec sources for this vintage model |
| Gradeability / rimpull | Not published in available spec sources for this vintage model |
Service capacities (summary)
| Fuel tank, hydraulic system, engine oil, cooling system | Fill capacities are not documented in publicly available spec sheets for this 1989-1995 vintage model — refer to the machine operation and maintenance manual or your dealer for exact figures |
Values vary by configuration, region, and serial range — confirm against your machine before planning transport or lifts.
D300D fluids & capacities
| System | Capacity | Recommended fluid |
|---|---|---|
| Fuel tank | Not published in accessible sources for this serial range (5MG1-up) — verify against the OMM or a Cat dealer. | Diesel fuel meeting Caterpillar's diesel fuel specification current for the 3306 DITA engine; use winter-grade blend in cold climates to prevent fuel waxing. |
| Cooling system | Not published in accessible sources for this serial range — verify against the OMM or a Cat dealer. | Caterpillar heavy-duty ethylene-glycol antifreeze/coolant at a 50/50 water blend, maintained with supplemental coolant additive on the service interval; this machine predates Cat Extended Life Coolant, so conventional coolant with SCA top-off applies. |
| Engine crankcase (with filter) | Not published in accessible sources for this serial range — verify against the OMM or a Cat dealer. | Caterpillar Diesel Engine Oil for the 3306 DITA (turbocharged, aftercooled, mechanically governed diesel). Multigrade SAE 15W-40 for temperate service; drop to SAE 10W-30 in cold-climate starts per Cat's oil-viscosity-by-ambient-temperature guidance of the era. |
| Transmission (powershift) | Not published in accessible sources for this serial range — verify against the OMM or a Cat dealer. | Caterpillar TDTO (Transmission/Drive Train Oil), multigrade; viscosity selected by ambient temperature per the OMM's cold-weather oil chart. |
| Front axle — differential and final drives | Not published in accessible sources for this serial range — verify against the OMM or a Cat dealer. | Caterpillar TDTO, same multigrade family as the transmission, selected by climate. |
| Center axle — differential and final drives | Not published in accessible sources for this serial range — verify against the OMM or a Cat dealer. | Caterpillar TDTO, same multigrade family as the transmission, selected by climate. |
| Rear axle — differential and final drives | Not published in accessible sources for this serial range — verify against the OMM or a Cat dealer. | Caterpillar TDTO, same multigrade family as the transmission, selected by climate. |
| Hydraulic system (total, incl. lines and cylinders) | Not published in accessible sources for this serial range — verify against the OMM or a Cat dealer. | Caterpillar hydraulic oil to Cat's system specification for this truck class; on this generation of Cat articulated truck the implement/steering circuit commonly draws from the same oil family as the power train — confirm against the OMM before mixing services. |
| Hydraulic tank (refill) | Not published in accessible sources for this serial range — verify against the OMM or a Cat dealer. | Same hydraulic oil as the hydraulic system above; check level at the tank sight gauge with the machine on level ground and the body lowered. |
| Grease (chassis lubrication points) | Spec only — no volume figure applies. | Caterpillar multipurpose grease, NLGI 2, lithium-complex base for general chassis, pins, and bushings; switch to an NLGI 1 or arctic-grade grease in sustained sub-freezing service per the OMM's climate guidance. |
Capacities are refill values from factory literature — always fill to the dipstick/sight gauge, not the number.
Caterpillar D300D maintenance schedule
| Service interval | Tasks |
|---|---|
| Every 10 h |
|
| Every 250 h |
|
| Every 500 h |
|
| Every 1,000 h |
|
| Every 2,000 h |
|
| Every 6,000 h |
|
Servicing the D300D beyond the schedule
Predictive Maintenance & Fluid Analysis
Since the 3306 DITA has no ECM or fault-code system, scheduled oil analysis is the main predictive tool on the D300D. Sample engine oil for coolant or fuel dilution and wear metals, pull transmission and axle samples to catch planetary final-drive wear early, and check hydraulic oil for pump wear debris. Test coolant strips for corrosion-inhibitor depletion. Watch turbo boost and exhaust temperature together - a drop in boost with rising temperature usually means a fouled aftercooler core before it costs real power.
Corrective & Common Repairs
Common wear points on the D300D center on the articulation hitch bushings and pins, which take constant twisting load on rough haul roads, and the oil-cooled disc brakes on the tandem rear bogie, which wear faster on grade work. Because the engine is mechanically governed, power loss or smoke changes usually trace back to injector condition or fuel-setting drift rather than a sensor fault. Also watch the turbocharger for shaft play from dusty pit air, and the driveshaft U-joints between the transfer case and the front, center, and rear axles.
Overhaul & Rebuild Points
At major overhaul, plan around 3306 DITA top-end work: injector and injection-pump recalibration, turbocharger core exchange, and cylinder liner and piston inspection typical of a mechanical direct-injection diesel. The powershift transmission clutch packs and the planetary final drives on the front, center, and rear axles are the next-biggest rebuild items on a truck that spends its life fully articulated on grade. Because the D300D shares core 3306 architecture with other Caterpillar machines of its era, remanufactured long blocks and injection components still come from the wider 3306 parts pool.
Seasonal & Environment Servicing
Cold-start prep matters on a mechanically governed diesel with no ECM-managed strategy: verify the cold-start aid, battery condition, and coolant freeze protection before winter. In hot, dusty pit or quarry service, shorten air-filter and aftercooler-fin cleaning cycles to protect the turbocharged 3306 from heat soak, and check the articulation joint and oil-cooled brakes more often since abrasive fines accelerate seal and pad wear. Wash mud and grit from the hitch and driveline U-joints regularly to keep grease points working and to catch leaks early.
D300D common service parts
| Part number | Part | Notes | |
|---|---|---|---|
| 8M-3182 | Spring,Helical,Comp Engine Oil Filter Assembly | Lubrication service | Check fitment → |
| 2P-2537 | Stud Engine Oil Filter | Lubrication service | Check fitment → |
Always confirm against your machine's serial number — cross-check any part in Heavy Parts AI before ordering.
D300D fault codes & troubleshooting
| Code | Meaning | Likely cause | What to do |
|---|---|---|---|
| Engine Oil Pressure warning lamp (red, oil-can symbol) + audible alarm | Engine oil pressure has dropped below the safe minimum for the running condition. | Low oil level, worn or failed oil pump, plugged filter, worn bearings, or a faulty oil pressure sending switch/wiring. | Idle down and shut the engine off if safe to do so; check oil level and filter condition before restart; check the sender and wiring if level and pressure test normal. |
| Engine Coolant Temperature warning lamp (red, thermometer symbol) + audible alarm | Coolant temperature has risen above the normal operating range. | Low coolant level, blocked radiator core or fins, failed fan drive or belt, stuck thermostat, or water pump failure. | Reduce load and let the engine idle to cool; once safely stopped check coolant level and clear debris from the radiator and fan; do not open a hot radiator cap. |
| Charging System warning lamp (amber/red, battery symbol) | Alternator output is not maintaining normal charging voltage on the battery circuit. | Loose or broken alternator belt, failed alternator, blown fuse, or a loose/corroded battery or ground connection. | Check belt tension and battery/ground connections; if the lamp stays on with the engine running, have the charging circuit tested before continuing to run on battery reserve. |
| Parking Brake indicator lamp | Parking brake is applied and engaged. | Normal indication when the park brake control is set; can also stay lit from a stuck control valve or switch if the brake will not release. | Confirm the brake control position; if the lamp stays lit with the control released, have the park brake circuit and valve checked before moving the truck. |
| Brake System low pressure warning lamp + buzzer | Hydraulic brake system pressure or accumulator charge has dropped below the safe minimum. | A leak in the brake circuit, a failed charging pump, or low hydraulic fluid feeding the brake system. | Stop the truck; do not continue operating with this alarm active; check fluid level and have the brake charging circuit inspected before further use. |
| Transmission/Torque Converter Oil Temperature warning lamp (amber/red) | Transmission or torque converter oil temperature has exceeded the normal operating range. | Low transmission fluid, a plugged oil cooler, sustained converter stall/lock-up operation, or a failed temperature sender. | Reduce work load and let the converter cool at low idle; once stopped, check fluid level and cooler airflow. |
| Body (dump bed) not fully lowered alarm/indicator | Dump body is not confirmed down and seated on the frame; warns the operator before road travel. | Body still raised or resting off the frame rails, or a fault in the body-lower solenoid or position switch circuit. | Fully lower and seat the body before traveling; if the lamp stays on with the body down, check the body-lower solenoid circuit and switch. |
| Low Fuel Level indicator lamp | Fuel level in the tank has dropped to the reserve range. | Normal low-fuel warning; can also be triggered by a faulty fuel level sender or float. | Refuel as soon as practical; if the lamp stays lit after refueling, check the fuel gauge sender and float. |
Codes and remedies are general guidance for this model family — always confirm with diagnostic tooling and your dealer before major repairs.
D300D attachments & work tools
Work-tool / attachment scope
The D300D is an articulated dump truck (hauler), not a tool-carrier, and has no quick-coupler or interchangeable work-tool system like an excavator or loader. Factory-level configuration for this class centers on the dump body, tailgate, tires, drivetrain, and guarding rather than swappable ground-engaging tools.
Dump body
Typical heaped body capacity for this size/payload class runs around 18 cubic meters, with a rated payload near 27.2 tonnes (about 59,965 lb / 27.3 tons). A heavier-gauge, wear-resistant liner body was the common alternative to the standard body for abrasive rock and quarry duty; the body is chassis-specific and bolted/pinned in place, not a field-swappable attachment.
Tailgate
Two tailgate styles are typical for this class: a hinged/pivoting tailgate that retains fine or wet material in transit, and an open or spreader-style tailgate used for controlled spreading of aggregate or fill. Choice depends on haul material and site use, not a bolt-on work tool, and is set at the body/chassis level.
Hydraulic hoist system
Body raise and lower is handled by double-acting hydraulic hoist cylinders fed off the truck's main hydraulic pump, separate from the steering circuit. Dump angle is around 55 degrees, sufficient for most heaped aggregate and rock loads; no rear-ejector body option is documented for this model or size class.
Tires
Reported standard tire sizes for this size/class span roughly 23.5-25 to 26.5-25 depending on source and axle loading; treat this as varies by configuration/series rather than one fixed spec. Both bias-ply and radial off-road tires were used across the era for this truck class.
Drivetrain and differential lock
The D300D runs a 6x6 all-wheel-drive layout with front, center, and rear axle differentials linked through a transfer gear case, per the machine's own service documentation. Cross-axle and inter-axle differential locks on trucks of this generation are engaged manually from an operator-compartment switch, predating Caterpillar's later automatic traction-control systems.
Cab guarding / ROPS-FOPS
A ROPS-certified operator cab is standard for this class. An overhead FOPS screen or rock-guard mesh was a common factory or dealer-fit option for quarry and blast-rock duty on trucks of this size, though availability by serial range is not separately documented for the D300D — confirm with a dealer for a specific unit.
All D300D assemblies by section
Every catalogued assembly group for the Caterpillar D300D. Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.
Basic Engine
284-7811 Kit-Hardware
| 0L***43 | Bolt 63.5 mm (3/8" X 2 1/2" -Cover Assembly To Fender | 1 |
| 0S***91 | Screw,Cap,Hexagon Bearing Retainer; Part Of Kit P/N 1w***82 | 2 |
| 0S***94 | Bolt (1 In. Long 3/8 In. Dia.); Plate Assembly To Support Assembly | 2 |
Engine Arrangement
284-3287 Conversion Ar-Engine
| 0R***14 | Rod As-Connecting | 1 |
| 0R***97 | Cylinder Pack Group | 6 |
| 0R***82 | Injector As | 6 |
Fuel System
7c-8993 Fastener Gp-Fuel Inj Pump
| 0S***14 | Bolt (.25" Diameter-.50" Long) | 3 |
| 2S***83 | Bolt (3.25" Long-Drilled Head) | 1 |
| 4F***57 | Screw,Cap,Hexagon H Shock Mount To Bracket | 8 |
111-5162 Control Gp-Fuel Ratio
| 10***93 | Washer | 1 |
| 11***62 | Control Group-Fuel Ratio (Basic) | 1 |
| 11***58 | Washer; (12.7x6.65x0.79-mm Thk) | 1 |
2w-2410 Governor Gp
| 03***16 | Bolt-Self Locking; (1/4unc X 3/4) | 3 |
| 0S***16 | Screw,Cap,Hexagon H Receptacle Mtg; Bolt Brackets To Firewall Assembly | 6 |
| 13***07 | Seal-Lip Type; (6.39mm) | 1 |
115-9595 Pump Gp-Fuel Injection
| 0S***15 | Bolt 19 mm (.75 In.) Long Return Air Console To Enclosed Rops | 4 |
| 11***18 | Seal-O-Ring; (26.64mm Id) | 6 |
| 11***95 | Pump Group-Fuel Injection | 1 |
4p-9827 Pump Gp-Fuel Injection
| 1W***87 | Valve As-Check; (Fuel Injection Pump) | 1 |
| 4P***27 | Pump Group-Fuel Injection | 1 |
| 4P***30 | Plunger & Barrel Assem. | 1 |
7c-8992 Seal Gp-Pump
| 03***79 | Seal-O-Ring (Id=10.82mm) | 1 |
| 14***77 | Gasket | 1 |
| 15***26 | Gasket | 1 |
1w-1597 Torque Control Gp
| 1P***52 | Insulator,Bushing Governor | 1 |
| 1W***97 | Torque Control Group | 1 |
| 2P***85 | Spacer (.635 mm Thk); (0.635-mm Thk) | 1 |
Service Equipment And Supplies
284-3299 Kit-Engine Parts
| 10***68 | Hose As | 1 |
| 10***69 | Tube As; (Oil) | 1 |
| 12***74 | Clip-Loop; (12.7mm Id) | 1 |
D300D serial number reference
The PIN plate on a D300D is riveted to the frame, typically on the front chassis rail near the articulation hitch or cab support post, and is stamped rather than a sticker on machines of this age. Read the first three characters as the prefix (identifies this model and its build series) and the digits after as the individual unit's sequence number; a plate reading 5MG00512 is unit 512 of the 5MG series. If the plate is missing or worn, the number is also stamped into the frame itself near the same location.
| Prefix | Identifies | Notes |
|---|---|---|
| 5MG | D300D articulated dump truck | Only PIN prefix documented for this model. The disassembly-and-assembly service guide, electrical system schematic, and parts book are all scoped to 5MG1-and-up (also written 5MG00001-and-up), covering the truck's full build run. No second or later-series prefix exists for this chassis. |
Frequently asked questions
What engine does the Caterpillar D300D use?
A Caterpillar 3306 DITA - turbocharged, aftercooled, direct-injection diesel with a fully mechanical fuel system. Gross output is documented between 194 and 213 kW (260-285 hp) depending on the source and rating method. There is no ECM or digital fault-code system on this engine; warnings are analog gauge and lamp based.
What is the operating weight of the Caterpillar D300D?
Empty operating weight runs about 20.7 tonnes (45,600 lb), with a rated payload near 27.2 tonnes (roughly 59,900-60,000 lb). Exact figures vary slightly by source and by body/tire configuration.
What replaced the Caterpillar D300D?
Caterpillar replaced the D300D with the D300E in 1996, which was later followed by the D300E II. The D300D itself had succeeded the earlier D300B in Caterpillar's D300 articulated-truck line.
What D300D owners discuss
How does the D300D's engine and transmission behave together in daily use?
Does this D300D share the cold-start and pre-chamber complaints people report for other 3306 engines?
What causes overheating or turbo/aftercooler complaints on these trucks?
What wear points show up around the hitch, oscillating axle, and tires?
What electrical or gauge issues come up most on a machine this age?
What does the dump box and hoist system typically need watching?
What should a buyer check before purchasing a used D300D?
Compiled from owner and technician discussions across the industry — experiences vary by serial range and machine history.
Need a specific D300D part?
Search live OEM part data, check fitment, and cross-reference alternatives with Heavy Parts AI.