Caterpillar D40D
Maintenance schedule, common problems & OEM parts breakdown
The Caterpillar D40D is a large articulated dump truck built for off-highway hauling in mining, quarry, and heavy earthmoving work. It shares its chassis and running gear with the D400D badge, the same machine sold under a metric-tonne payload designation rather than the D40D's US-ton naming. Power comes from a Cat 3406 or 3406B mechanical-injection inline-six diesel rated at roughly 287 kW (385 hp) gross from 14.6 L (891 cu in) displacement, driving a 4-speed powershift transmission through a fully oscillating articulation hitch. Empty weight runs around 28,027 kg (61,789 lb), with a rated payload near 36,281 kg (79,986 lb) and a loaded operating weight close to 64,308 kg (141,775 lb). Production spanned roughly the late 1980s into the mid-1990s, carrying serial prefixes 2JJ on earlier units and 8TF on later ones, before the line was succeeded by the D400E. Body capacity is quoted anywhere from about 22 to 29 m3 heaped depending on body and tailgate configuration.
Across its production run the D40D/D400D changed mainly in running production detail rather than in a wholesale redesign, moving from the 2JJ-prefix build to the 8TF-prefix build with the same 3406B mechanical engine, powershift transmission, and wet, oil-cooled disc brakes sharing a common TDTO circuit. The 8TF-prefix trucks are the ones most commonly documented in later service literature and are the more common survivors in the field. The bigger break in the lineage came with the D400E, which moved to an electronically governed 3406E and left the D40D/D400D as the last fully mechanical truck in this size class before Cat's ADTs went electronic. That mechanical simplicity is exactly why the D40D still matters in the used and parts market today: no ECM, no electronic diagnostics to fail, and a driveline, hitch, and wet-brake system that a field mechanic can service and rebuild without a factory service tool. Surviving units are valued as rebuildable haul trucks and as a source of chassis, hitch, and brake components for shops supporting this generation of Cat ADT.
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 D40D specifications
Engine
| Engine model | Cat 3406, inline-six diesel |
| Gross power | 287 kW (385 hp) |
| Net power | Not published in available spec sheets |
| Displacement | 14.6 L (891 cu in) |
| Cylinders | 6, inline |
| Emissions tier | Not applicable — machine built 1989-1994, predates off-highway emissions tier regulation |
Weights
| Operating weight (empty) | 28,027 kg (61,789 lb), rounded to approx. 28,100 kg (62,000 lb) in some listings |
| Rated payload | 36,281 kg (79,986 lb) |
| Gross weight (loaded) | 64,308 kg (141,775 lb) |
| Ground pressure | Not published |
Dimensions
| Overall length | 9.78 m (32 ft 1 in) |
| Overall width | 3.47 m (11 ft 5 in) |
| Overall height | 3.57 m (11 ft 8 in) |
| Wheelbase | 4.88 m (16 ft) |
| Body raised (dump) height | 5.52 m (18 ft 1 in) |
| Tire size | Front 29.5x25 radial, rear 33.25x29 radial |
| Ground clearance | Not published |
Performance
| Maximum travel speed | 55 km/h (34.2 mph) |
| Transmission | Powershift, 4 forward gears |
| Body capacity, heaped | 22.4 m³ (29.3 cu yd) |
| Body capacity, struck | 17.0 m³ (22.2 cu yd) |
| Gradeability | Not published |
Service capacities (summary)
| Fuel tank | 450 L (118.9 gal) |
| Engine oil | Not documented for this machine's installation — verify with dealer/service manual |
| Cooling system | Not documented for this machine's installation — verify with dealer/service manual |
| Hydraulic system | Not documented for this machine's installation — verify with dealer/service manual |
Values vary by configuration, region, and serial range — confirm against your machine before planning transport or lifts.
D40D fluids & capacities
| System | Capacity | Recommended fluid |
|---|---|---|
| Engine crankcase (3406B inline-6, with oil filter) | approx. 30 L (7.9 US gal) refill; some 3406B truck sump configurations run up to 38-40 L (10-10.5 US gal) - varies by configuration/series | Cat DEO (Diesel Engine Oil). SAE 10W-30 for cold-climate starts, SAE 15W-40 for temperate/warm climates, per Cat's ambient-temperature viscosity guidance. |
| Cooling system | Not documented in available sources for this serial range - verify against the OMM or with your dealer | Cat heavy-duty coolant/antifreeze with corrosion inhibitor for this production era (predates Cat ELC); check glycol/inhibitor concentration with a coolant test kit at scheduled intervals. |
| Fuel tank | 450 L (118.9 US gal) | No. 2-D diesel meeting Cat's fuel specification; low-sulfur diesel, minimum cetane number 40. Use No. 1-D or a winter blend in cold climates to prevent fuel waxing. |
| Powershift transmission | approx. 130 L (34.3 US gal) - single-sourced figure, not independently cross-verified; confirm against the OMM for your exact serial prefix | Cat TDTO (Transmission/Drive Train Oil). SAE 10W in cold weather, SAE 30 in warmer climates. |
| Differentials/axles - front, center (inter-axle), and rear | Front approx. 38 L (10.0 US gal); center approx. 38 L (10.0 US gal); rear approx. 40.8 L (10.8 US gal) - varies by configuration/series, not independently cross-verified | Cat TDTO, or a gear lubricant meeting GL-5 performance, SAE 80W-90 up to 85W-140 depending on ambient temperature. |
| Transfer gearbox | approx. 2.5 L (0.7 US gal) | Cat TDTO, SAE 10W or SAE 30 grade depending on climate. |
| Hydraulic system (hoist and steering circuit, incl. tank) | approx. 203 L (53.6 US gal) system/tank total - single-sourced figure, confirm against the OMM | Cat TDTO or Cat's multi-purpose tractor/hydraulic oil for this vintage of machine (dedicated Cat HYDO Advanced was not the standard spec for this era); viscosity graded by ambient temperature same as transmission oil. |
| Brake system (wet, oil-cooled multiple-disc) | No separate brake-fluid reservoir; brakes are cooled and lubricated by the drivetrain oil circuit, not a dedicated hydraulic-brake-fluid system | Same oil as the transmission/final-drive circuit - Cat TDTO. |
| Grease points (chassis pins, bushings, articulation joint) | Spec only - no single system capacity; apply per lubrication schedule until purged | Cat Multipurpose Grease (Cat MPGM), NLGI 2 for general chassis points; Cat Advanced 3Moly grease for high-load pin and bushing joints, especially the articulation hitch. |
Capacities are refill values from factory literature — always fill to the dipstick/sight gauge, not the number.
Caterpillar D40D maintenance schedule
| Service interval | Tasks |
|---|---|
| Every 10 h |
|
| Every 50 h |
|
| Every 250 h |
|
| Every 500 h |
|
| Every 1,000 h |
|
| Every 2,000 h |
|
| Every 4,000 h |
|
| Every 6,000 h |
|
Servicing the D40D beyond the schedule
Predictive Maintenance & Fluid Analysis
Run regular oil sampling on the 3406B to track blow-by and oil consumption trends before they become a bottom-end problem; this engine has no ECM to flag deterioration electronically. Sample the shared wet-brake/TDTO circuit oil separately, since brake, hitch, and driveline components draw from the same fluid and contamination shows up there first. Track powershift clutch pack condition through transmission oil analysis, since wrong-viscosity fluid is the leading cause of premature clutch-pack wear on this machine.
Corrective & Common Repairs
Expect recurring wear at the articulation hitch bushings on a fully oscillating frame; inspect for play at every service interval and regrease on schedule. Check gauge sender wiring and harness routing near the hitch for chafing, a known nuisance-fault source on these trucks. Watch the dump-body hydraulic circuit for cylinder drift with the body raised, and address powershift clutch slip or delayed shifts promptly, since both point back to fluid condition rather than a single bad component.
Overhaul & Rebuild Points
Plan engine overhauls around the 3406B's mechanical injection pump timing, valve lash, and blow-by trend rather than a fixed calendar, since there is no electronic diagnostic layer to prompt one. The powershift transmission and wet-disc brake packs are the other major rebuild items on this chassis; both wear against the same TDTO circuit condition. Hitch pins and bushings on the oscillating articulation joint are a wear item worth budgeting for as a full-set replacement rather than piecemeal.
Seasonal & Environment Servicing
In dusty quarry or mine environments, service the air cleaner and radiator core more often than the base interval and inspect the fuel/water separator closely, since the mechanical injection pump on the 3406B is unforgiving of contaminated fuel. In cold climates, use the correct viscosity oil in the transmission and wet-brake circuit, since low-temperature thickening is a known driver of clutch-pack wear on this machine. Keep hitch and pivot grease points serviced more frequently when working in mud or standing water to protect the bushings.
D40D fault codes & troubleshooting
| Code | Meaning | Likely cause | What to do |
|---|---|---|---|
| Engine Oil Pressure warning lamp (red) | Engine oil pressure has dropped below the safe operating minimum | Low oil level, worn oil pump, plugged oil filter, or a faulty pressure sending unit | Stop the engine immediately, check oil level and filter condition, and verify the sender before restarting |
| Coolant Temperature warning lamp / gauge in red zone | Engine coolant temperature has exceeded the safe operating range | Low coolant level, blocked radiator core, slipping or broken fan drive belt, or a stuck thermostat | Reduce load and idle the engine down, then check coolant level, belt condition, and radiator airflow before continuing |
| Charging System warning lamp | Alternator output or battery charging circuit is out of range | Loose or broken alternator belt, faulty alternator, or a wiring/connection fault | Check belt tension and battery terminal connections, then test alternator output |
| Parking Brake indicator lamp | Parking brake is applied or brake system has not fully released | Park brake control left engaged, or low hydraulic/air pressure feeding the brake release circuit | Confirm brake control position and check brake system charge pressure before moving the truck |
| Transmission Oil Temperature warning (gauge) | Transmission or torque converter oil temperature is above normal operating range | Low transmission fluid level, restricted oil cooler, or sustained lugging on grade | Reduce load or shift to a lower gear, then check fluid level and cooler flow once safely stopped |
| Air Filter Restriction indicator | Intake air filter restriction has exceeded the allowable limit | Clogged primary air filter element | Service or replace the air filter element per the restriction gauge reading |
| Secondary/Service Brake Low Pressure warning lamp | Brake system accumulator or supply pressure has dropped below the safe threshold | Compressor or charging pump fault, system leak, or insufficient accumulator charge time | Do not move the truck until pressure is restored; inspect the brake charging circuit for leaks or pump failure |
Codes and remedies are general guidance for this model family — always confirm with diagnostic tooling and your dealer before major repairs.
D40D attachments & work tools
Payload / dump body class
40-ton class articulated hauler. Rated payload runs about 36-40 t (79,000-80,000 lb). Heaped body volume is reported across a wide range, roughly 22-29 m3 (29-38 yd3), depending on source and body configuration.
Dump body and tailgate
Standard full-height tailgate is fitted for normal spoil and aggregate work. A half-height tailgate is offered as a factory/dealer option for free-flowing or fine material that does not need full containment.
Body liner and sideboards
As with other Cat haul bodies in this size class, impact/wear liner kits, sideboards, and tail extensions are offered to protect the floor from abrasive loads and add heaped volume for lighter material. Not documented against this exact serial range - verify with a dealer for the D40D specifically.
Articulation hitch (coupling)
Front and rear frame halves join through a fully oscillating hitch rather than a bucket-style quick coupler. This hitch and steering arrangement is shared across the wider D25D, D30D, D350D, D40D and D400D family per the factory steering service documentation for that group.
Engine / powertrain
Factory-fitted with the Cat 3406B diesel, about 287 kW (385 hp) gross, per the engine service manual issued specifically for the D40D and D400D pairing. No alternate engine option is documented for this model.
Tires
Radial tires are fitted front and rear in different sizes for this class, roughly 29.5x25 front and 33.25x29 rear. Older units in the series may carry bias-ply equivalents; confirm against the specific serial prefix.
Automatic/central lubrication
Central chassis lubrication was available as a factory option on earlier production of this family. Reporting on the closely related D400D indicates the option was dropped from the lineup by the mid-1990s; confirm availability for a specific D40D serial range with your dealer.
All D40D assemblies by section
Every catalogued assembly group for the Caterpillar D40D. Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.
Basic Engine
333-1672 Kit-Engine Parts
| 06***40 | Seal-O-Ring (Id=37.69mm) | 1 |
| 0T***00 | Plug (.5625" Diameter) | 1 |
| 10***47 | Cover-Flyweight | 1 |
321-1454 Kit-Hardware
| 00***01 | Ring-Retaining | 1 |
| 0S***94 | Bolt (1 In. Long 3/8 In. Dia.); Plate Assembly To Support Assembly | 8 |
| 0T***65 | Bolt--3/8" X 3 1/2"--Use As Required; Bolt 5t***56 Plate To Cover Gp 4n***72 | 8 |
Engine Arrangement
333-1671 Conversion Ar-Engine
| 03***79 | Seal-O-Ring (Id=10.82mm) | 1 |
| 0R***39 | Pin-Piston | 1 |
| 0R***81 | Rod As-Connecting | 1 |
Fuel System
124-5658 Control Gp-Fuel Ratio
| 10***93 | Washer | 1 |
| 11***58 | Washer; (12.7x6.65x0.79-mm Thk) | 1 |
| 12***57 | Spring-Fuel Ratio Control | 1 |
9y-4913 Fastener Gp-Fuel Inj Pump -Governor
| 1B***16 | Bolt; (1/4-20x5-In) | 2 |
| 4F***57 | Screw,Cap,Hexagon H Shock Mount To Bracket | 2 |
| 5P***37 | Washer 5t***54 Plate To 7t***28 Cable As | 2 |
7c-4797 Governor Gp
| 03***16 | Bolt-Self Locking; (1/4unc X 3/4) | 3 |
| 0S***47 | Bolt; (1/4-20x0.75-In)(Drilled Head) | 2 |
| 0S***88 | Bolt,Machine; Hose Assembly Mounting,Hose Assembly To Transmission,And To Torque Converter | 1 |
108-6633 Pump Gp-Fuel Injection
| 10***02 | Bonnet-Valve | 1 |
| 10***04 | Plunger & Barrel As | 1 |
| 10***33 | Pump Group-Fuel Injection | 1 |
111-9363 Pump Gp-Fuel Injection
| 0S***15 | Bolt 19 mm (.75 In.) Long Return Air Console To Enclosed Rops | 14 |
| 10***33 | Pump Group-Fuel Injection | 6 |
| 10***06 | Seal-O-Ring (10.52mm Id) | 1 |
126-6710 Torque Control Gp
| 12***91 | Spring-Torque; (0.254-mm Thk) | 1 |
| 12***10 | Torque Control Group | 1 |
| 1P***52 | Insulator,Bushing Governor | 1 |
D40D serial number reference
The PIN/serial plate on this articulated truck is riveted to the frame rather than the engine. The plate lists the model designation plus the serial number; the first three characters (a mix of digits and letters, e.g. 2JJ or 8TF) are the prefix that ties the unit to its production series, and the digits that follow are the sequential unit number within that series. Exact plate placement is not documented for this specific model - verify with your dealer or the machine's operation and maintenance manual.
| Prefix | Identifies | Notes |
|---|---|---|
| 2JJ | D40D / D400D articulated truck, earlier build series | Runs from 2JJ00001 up. Fitted with the 3406 diesel (turbocharged inline-six). Falls in the machine's earlier production window, roughly late 1980s into the early 1990s. Factory manuals cover this prefix under both the D40D and D400D badges together, so the same unit range answers to either name depending on the market. |
| 8TF | D40D / D400D articulated truck, later build series | Runs from 8TF00001 up. Fitted with the 3406 diesel. Falls in the machine's later production window, into the mid-1990s, ending when the D400E took over the line. Same dual-badge pattern as 2JJ: one prefix, sold as D40D or D400D depending on region. |
Frequently asked questions
What engine powers the Caterpillar D40D?
A Cat 3406 or 3406B mechanical-injection inline-six diesel of 14.6 L (891 cu in) displacement, rated at roughly 287 kW (385 hp) gross. It predates the electronically governed 3406E and carries no ECM.
What is the D40D's operating weight?
Empty weight is about 28,027 kg (61,789 lb). Rated payload is about 36,281 kg (79,986 lb), bringing loaded operating weight to roughly 64,308 kg (141,775 lb).
What replaced the Caterpillar D40D?
The D400E succeeded the D40D/D400D, moving the same size class of articulated truck to an electronically governed 3406E engine.
What D40D owners discuss
What do experienced operators say about the D40D's engine and powershift transmission behavior?
What undercarriage or structural wear pattern is most talked about on this truck?
Are there any engine quirks specific to the 3406/3406B series in this truck?
What electrical or sensor issues come up most often on trucks this age?
What causes the dump body to stop responding, and is it usually a quick fix?
What should owners watch for with the wet, oil-cooled disc brakes?
What should a buyer check before purchasing a used D40D?
Compiled from owner and technician discussions across the industry — experiences vary by serial range and machine history.
Need a specific D40D part?
Search live OEM part data, check fitment, and cross-reference alternatives with Heavy Parts AI.