Caterpillartrack-type tractor

Caterpillar D6H

Maintenance schedule, common problems & OEM parts breakdown

The Caterpillar D6H is a medium bulldozer introduced in 1986 as part of the H-Series track-type tractor line. It succeeded the D6D and was replaced by the D6R in 1996. The machine is powered by the Caterpillar 3306 engine, producing 165 hp (123 kW) gross power with a displacement of 640.7 cu in (10.5 L). Operating weights range from 39,156 lb (17,761 kg) for standard configurations to 43,682 lb (19,814 kg) for the LGP Series II. Configurations include standard, low ground pressure (LGP), and Series II variants, offering straight, universal, and power angle tilt blade options.

The D6H introduced Caterpillar's first elevated drive sprocket undercarriage for the D6 class, improving durability and track life compared to the D6D. It remains significant in the used market due to its robust 3306 engine and widespread parts availability. The machine's transition from the D6D to the D6R marks a key generation shift in Caterpillar's medium dozer lineup, with the D6H serving as a bridge between older mechanical systems and the more advanced electronics of the D6R. Its continued presence in forestry, agriculture, and construction sectors highlights its versatility and serviceability.

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 D6H specifications

Engine

Model	Caterpillar 3306
Configuration	10.5 L (640.8 cu in) 6-cylinder diesel, turbocharged
Gross Power	179 hp (133.5 kW) at 1800 rpm (D6H); 165 hp (123.0 kW) at 1800 rpm (D6H Series II); 170 hp (126.8 kW) at 1800 rpm (D6H LGP Series II)
Net Power	165 hp (123.0 kW)

Weights

Operating Weight (Std)	39156.4 lb (17761.0 kg) to 40000 lb (18144 kg) varies by configuration/series
Operating Weight (LGP)	43354 lb (19665 kg) to 43682.4 lb (19814 kg) varies by configuration/series
Weight Range (General)	30359 lb to 39325 lb (13768 kg to 17837 kg) varies by configuration/series

Dimensions

Length w/ Blade	16.44 ft (5010 mm) to 16.99 ft (5176 mm) varies by configuration/series
Length w/o Blade	13.33 ft (4060 mm) to 14.72 ft (4485 mm) varies by configuration/series
Width Over Tracks	7.68 ft (2340 mm) to 10.31 ft (3140 mm) varies by configuration/series
Height to Top of Cab	10.24 ft (3138 mm) to 10.3 ft (3139 mm) varies by configuration/series
Length of Track on Ground	8.6 ft (2620 mm) to 10.72 ft (3265 mm) varies by configuration/series
Ground Clearance	1.24 ft (376 mm) to 1.26 ft (382 mm) varies by configuration/series
Track Gauge	6.17 ft (1880 mm) to 7.3 ft (2225 mm) varies by configuration/series
Standard Shoe Size	22.05 in (560 mm) to 36.03 in (915 mm) varies by configuration/series
Ground Pressure	4.63 psi (31.9 kPa) to 8.56 psi (59 kPa) varies by configuration/series
Ground Contact Area	4557.01 in² (2.9 m²) to 9252 in² (6 m²) varies by configuration/series
Number of Track Rollers Per Side	6 to 8 varies by configuration/series
Number of Shoes Per Side	45

Performance

Max Speed Forward	7.1 mph (11.3 km/h) to 11.3 km/h varies by configuration/series
Max Speed Reverse	9 mph (14.4 km/h) to 14.5 km/h varies by configuration/series
Transmission Type	Planetary powershift
Forward Gears	3
Reverse Gears	3
Final Drives	Single-reduction planetary

Blades

Standard Blade Width	11.1 ft (3360 mm) to 13.1 ft (3990 mm) varies by configuration/series
Standard Blade Height	43.3 in (1098 mm) to 49.5 in (1257 mm) varies by configuration/series
Standard Blade Capacity	3.7 m³ (4.9 yd³) to 5.1 yd³ (3.9 m³) varies by configuration/series
Cutting Depth	18.6 in (472 mm) to 25.9 in (656 mm) varies by configuration/series

Service Capacities

Fuel Capacity	85.1 gal (322 L) to 89.1 gal (337.3 L) varies by configuration/series
Hydraulic Fluid Capacity	12.2 gal (46.2 L) to 19.2 gal (72.7 L) varies by configuration/series
Engine Oil Capacity	7.3 gal (27.5 L)
Cooling System Capacity	10.1 gal (38 L)
Final Drive Fluid Capacity	3.5 gal (13.2 L)
Hydraulic Pump Flow	19.3 gal/min (73 L/min) to 46.7 gal/min (176.8 L/min) varies by configuration/series
Relief Valve Pressure	2875 psi (198.2 bar) to 2871 psi (198.0 bar)

Values vary by configuration, region, and serial range — confirm against your machine before planning transport or lifts.

D6H fluids & capacities

System	Capacity	Recommended fluid
Engine Crankcase (w/ filter)	27.5 L (7.3 gal)	Cat DEO or DEO-ULS; SAE 15W-40 or 10W-30; SAE 30 or 40 for monograde applications. Viscosity selection depends on ambient temperature: use lower viscosity grades for cold climates and higher viscosity grades for hot climates per the Caterpillar Machine Fluids Recommendations guide.
Cooling System	Not documented for this exact serial range — verify with your dealer	Not documented for this exact serial range — verify with your dealer
Fuel Tank	337.3 L (89.1 gal)	Not specified
Transmission/Powertrain (Powershift)	Not documented for this exact serial range — verify with your dealer	Cat TDTO or fluid meeting Cat TO-4 specification. Viscosity selection depends on ambient temperature: use lower viscosity grades for cold climates and higher viscosity grades for hot climates per the Caterpillar Machine Fluids Recommendations guide.
Transmission/Powertrain (Bevel Gear/Steering)	Not documented for this exact serial range — verify with your dealer	Fluid meeting Cat TO-4 specification; SAE 50. Viscosity selection depends on ambient temperature: use lower viscosity grades for cold climates and higher viscosity grades for hot climates per the Caterpillar Machine Fluids Recommendations guide.
Final Drives (each)	Not documented for this exact serial range — verify with your dealer	Fluid meeting Cat TO-4 specification; SAE 50. Viscosity selection depends on ambient temperature: use lower viscosity grades for cold climates and higher viscosity grades for hot climates per the Caterpillar Machine Fluids Recommendations guide.
Hydraulic System/Tank	46.2 L (12.2 gal)	Cat HYDO Advanced or biodegradable hydraulic oil. Viscosity selection depends on ambient temperature: use lower viscosity grades for cold climates and higher viscosity grades for hot climates per the Caterpillar Machine Fluids Recommendations guide.
Pivot Shaft	Not documented for this exact serial range — verify with your dealer	Not documented for this exact serial range — verify with your dealer
Grease	Not applicable	Cat Multipurpose Grease for low-load/low-speed; Cat Advanced 3Moly Grease for medium-load/medium-speed; Cat Ultra 5Moly Grease for high-load/high-speed. Use Cat Arctic Platinum Grease for cold weather and Cat Desert Gold Grease for hot weather applications.

Capacities are refill values from factory literature — always fill to the dipstick/sight gauge, not the number.

Caterpillar D6H maintenance schedule

Service interval	Tasks
Every 10 h	Check engine oil level. Check hydraulic fluid level. Check coolant level. Drain water from fuel separator. Check air filter restriction indicator. Inspect for fluid leaks.
Every 250 h	Change engine oil and filter. Replace fuel filter element. Clean or replace air filter primary element. Check transmission oil level. Check final drive oil level. Grease all pivot points.
Every 500 h	Change transmission oil and filter. Change final drive oil. Replace hydraulic return filter. Test coolant SCA concentration. Inspect undercarriage wear. Check battery electrolyte level.
Every 1,000 h	Take hydraulic oil sample. Take engine oil sample. Inspect turbocharger condition. Torque ROPS bolts. Measure undercarriage component wear. Inspect cutting edge and end bits.
Every 2,000 h	Change hydraulic system oil. Flush and refill coolant system. Inspect structural welds. Inspect radiator and oil cooler fins. Check brake system components. Inspect all hoses and clamps.

Servicing the D6H beyond the schedule

Predictive Maintenance & Fluid Analysis

Monitor engine oil, hydraulic fluid, and coolant via Scheduled Oil Sampling (S.O.S) at 1,000-hour intervals. Check for water contamination in hydraulic oil, which causes pump cavitation. Analyze engine oil for fuel dilution and soot loading to prevent 3306 engine wear. Inspect coolant SCA concentration at 500 hours to prevent liner pitting. Track transmission oil condition to detect gear wear metals early. Use Cat DEO engine oil and HYDO Advanced hydraulic fluid to maintain system integrity and extend drain intervals.

Corrective & Common Repairs

Address transmission overheating by cleaning the oil cooler and checking the transmission oil temperature sensor. Replace worn track rollers and idlers to prevent undercarriage failure. Inspect the 3306 engine for valve clearance issues and injector wear. Check hydraulic relief valve pressure at 198.2 bar (2875 psi) to ensure proper blade control. Replace fuel filter elements every 250 hours to protect the injection pump. Inspect brake system components for wear and adjust as needed to maintain stopping power.

Overhaul & Rebuild Points

Plan major component overhaul at 20,000 hours or based on fluid analysis trends. Rebuild the 3306 engine when compression drops below specification or oil consumption exceeds limits. Replace the entire undercarriage when sprocket teeth are worn or track links are stretched. Overhaul the torque converter and transmission if slippage occurs or metal particles are found in oil. Inspect the hydraulic pump and control valves for internal leakage. Check structural welds on the frame and push arms for fatigue cracks.

Seasonal & Environment Servicing

In dusty environments, clean radiator and oil cooler fins daily and replace air filter elements more frequently. Use Cat Arctic Platinum grease in cold weather to prevent lubricant thickening. In hot climates, monitor hydraulic oil temperature and consider extended cooling intervals. Drain water from the fuel separator daily in humid conditions to prevent microbial growth. Check battery electrolyte levels and charge state before winter storage. Inspect all hoses and clamps for heat damage in high-temperature applications.

D6H fault codes & troubleshooting

Code	Meaning	Likely cause	What to do
MID 036 CID 0110 FMI 03	Engine Coolant Temperature Sensor — Voltage Above Normal	Open circuit in sensor wiring or failed sensor element	Inspect wiring harness for damage; replace sensor if circuit is intact
MID 036 CID 0190 FMI 08	Engine Speed Sensor — Abnormal Frequency	Speed sensor air gap error, sensor failure, or tone ring damage	Check sensor gap; test speed sensor and tone ring integrity
MID 036 CID 0041 FMI 03	8-Volt DC Supply — Voltage Above Normal	Short to power on the 8-volt reference circuit	Inspect sensors sharing the 8-volt supply and isolate the fault
MID 036 CID 0041 FMI 04	8-Volt DC Supply — Voltage Below Normal	Short to ground on the 8-volt reference circuit	Disconnect sensors one at a time to locate the short
MID 036 CID 0262 FMI 04	5-Volt Supply — Voltage Below Normal	Short to ground on the 5-volt reference circuit	Disconnect sensors one at a time to locate the short
MID 036 CID 0248 FMI 09	CAT Data Link — Abnormal Update Rate	CAN bus wiring damage or termination fault	Check CAN wiring and measure termination resistance
MID 036 CID 0091 FMI 02	Throttle Position Sensor — Erratic, Intermittent, or Incorrect	Faulty sensor or intermittent wiring connection	Check wiring connections; replace sensor if necessary
MID 036 CID 0168 FMI 01	System Voltage — Below Normal	Charging system issue or low battery voltage	Check alternator output and battery condition

Codes and remedies are general guidance for this model family — always confirm with diagnostic tooling and your dealer before major repairs.

D6H attachments & work tools

Blades

The D6H supports S, SU, and U blade types, with PAT (Power Angle Tilt) availability varying by configuration and series. Typical widths range from 2.34 m (92.4 in) over tracks to 2.59 m (102 in) for wider options, with capacities varying by blade style and machine weight.

Rippers

Multi-shank and single-shank rippers are available for the D6H class, with weights varying significantly by shank count and configuration. Factory specifications do not list a single ripper weight; values depend on the specific ripper model and machine serial prefix.

Winches

Hydraulic winches are available for towing and pulling applications, particularly for forestry configurations. Towing winch options vary by configuration, with specific capacities and mounting details dependent on the machine's serial number and rear attachment setup.

Drawbars/Counterweights

Drawbars and CCU (Cable Control Unit) mounts are available for pulling towed scrapers and trailed implements. Counterweights are offered as large steel slabs to add rear weight for heavy dozing, with specific weights varying by configuration and series.

Cab/ROPS Guarding

Four-post ROPS is standard, with an enclosed cab available as an option including air conditioning. Forestry and waste configurations require specific guarding options, which vary by configuration and series to meet operational safety standards.

Hydraulic Arrangement

The D6H uses a load-sensing hydraulic system with a pump flow of 167.3 LPM (44.2 GPM) for standard models and 176.8 LPM (46.7 GPM) for Series II. Front and rear tool hydraulic connections vary by configuration, with relief valve pressure set at 198.2 bar (2875 psi).

All D6H assemblies by section

Every catalogued assembly group for the Caterpillar D6H. Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.

Basic Engine

268-3748 Kit-Engine Parts

11***18	Tube As-Fuel Ratio	1
11***28	Elbow; (90-Deg)	1
12***94	Bolt-Tamperproof; (28.58mm)	1
12***96	Bolt-Tamperproof; (95.25mm)	1

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284-7808 Kit-Hardware

0L***43	Bolt 63.5 mm (3/8" X 2 1/2" -Cover Assembly To Fender	1
0S***71	Screw,Cap,Hexagon; Tube Assembly To Turbocharger And Elbow Mounting	3
0S***91	Screw,Cap,Hexagon Bearing Retainer; Part Of Kit P/N 1w***82	1
0S***94	Bolt (1 In. Long 3/8 In. Dia.); Plate Assembly To Support Assembly	2

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Engine Arrangement

267-5717 Conversion Ar-Engine

0R***14	Rod As-Connecting	1
0R***24	Nozzle As-Fuel Injection	6
0R***88	Cylinder Pack Group	6
10***21	Turbocharger Group	1

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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
4N***61	Bolt 165.1 mm(6.5 In.) Long	4

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1w-8668 Torque Control Gp

1P***52	Insulator,Bushing Governor	1
1W***68	Torque Control Group	1
2P***85	Spacer (.635 mm Thk); (0.635-mm Thk)	1
2W***34	Bar-Load Stop; (4.0mm Thk)	1

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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
2A***46	Bolt,Machine Governor Linkage Bracket	2

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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
15***28	Gasket-Governor	1

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111-3769 Pump Gp-Fuel Injection

0S***15	Bolt 19 mm (.75 In.) Long Return Air Console To Enclosed Rops	4
11***69	Pump Group-Fuel Injection	1
11***70	Camshaft Group	1
11***71	Camshaft-Fuel Pump	1

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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
6I***27	Bonnet-Valve	1

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7c-8992 Seal Gp-Pump

03***79	Seal-O-Ring (Id=10.82mm)	1
14***77	Gasket	1
15***26	Gasket	1
15***27	Gasket-Fuel	1

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D6H serial number reference

The Product Identification Number (PIN) plate is located on the rear of the machine, high on the left side of the frame rail, often near the end of the left track frame. For the D6H, the serial number consists of the last 8 characters of the 17-character PIN, beginning with a 3-character alphanumeric prefix followed by a 5-digit sequence ID.

Prefix	Identifies	Notes
4GG	D6H	Identified in operation and maintenance manual documentation for the D6H track-type tractor. Source coverage limited to this single prefix example; verify with dealer for full range.
4RC	D6H	Identified in operation and maintenance manual documentation for the D6H track-type tractor. Source coverage limited to this single prefix example; verify with dealer for full range.
4YF	D6H Track-Type Tractor / Powershift	Identified in service repair manual for D6H Track-Type Tractor, Powershift configuration. Covers serial number 4YF04000 and up. Engine: 3306.

Frequently asked questions

What engine does the Caterpillar D6H use?

The Caterpillar D6H uses the Caterpillar 3306 engine, producing 165 hp (123 kW) gross power with a displacement of 640.7 cu in (10.5 L).

What is the operating weight of the D6H?

Operating weight varies by configuration: 39,156 lb (17,761 kg) for standard models and up to 43,682 lb (19,814 kg) for the LGP Series II.

What model replaced the D6H?

The Caterpillar D6R replaced the D6H in 1996.

What D6H owners discuss

How does the D6H differential steer compare to clutch steer for precision work?

Operators describe the differential steer as 'nippy' and well-balanced, making it excellent for trimming and fine grading. It allows for precise control, often getting within an inch or two of grade pegs without needing a grader. However, it is not as effective as clutch steer in hard, difficult materials where extra weight and direct mechanical lock-up are required for pushing power. Early models may lack differential steer entirely; verify configuration by serial number prefix. Have your dealer verify the specific steering type for the unit in question before purchase.

What are the common undercarriage wear patterns and structural issues for the D6H?

Track frames are prone to cracking, particularly at weld points, and may require welding repairs that can recracked over time. Equalizer bars often develop play (reported around 1 inch) and are difficult to remove for repair on Series II models. The XL variant with seven rollers is generally preferred over the six-roller standard frame for durability. Idler wheels are frequently welded and thinned due to wear. Check track pad thickness and pin/sprocket wear, as pads may retain only 20 percent life even if other components appear functional.

What engine series powers the D6H and what are its known quirks?

The D6H uses the Caterpillar 3306 engine. Displacement is 640.7 cubic inches (10.5 L). Net horsepower varies by configuration: standard models produce 165 hp, while XL variants produce 175 hp. Some sources cite gross power at 170 hp or 179 hp depending on the specific rating standard (ISO/SAE vs. gross). The engine is robust but requires careful monitoring of oil levels to prevent starvation during high-load operations. Black smoke and power loss can indicate injector pump or timing issues, even if turbo and exhaust are clear.

What are the typical hydraulic and transmission cooling issues?

Transmission overheating is a common complaint, often linked to clogged transmission oil coolers or insufficient flow. The radiator features a 12-core V-shaped design with thin cores that easily clog, restricting airflow and causing engine and hydraulic overheating. The transmission cooler may be mounted vertically or horizontally depending on the configuration; horizontal mounts are harder to access. Clean the cooler and verify the transmission filter is not plugged. Use Cat TDTO fluid for the transmission and HYDO Advanced for hydraulics to prevent sludge and cavitation.

What electrical or sensor issues are frequently reported?

Operators report that the forward-to-reverse handle can become stiff to turn, potentially requiring lubrication or linkage adjustment. Gauges may fail or provide inaccurate readings; ensure all gauges are functional during inspection. Transmission overheating alarms may trigger due to plugged filters or sensor errors. Verify the integrity of the transmission oil temperature sensor and ensure fluid levels are correct, as low oil causes pressure drops and bearing damage.

What is the recommended fluid specification for the D6H transmission and hydraulics?

Transmission fluid must meet Cat TO-4 specification. Hydraulic fluid should be Cat HYDO Advanced or equivalent biodegradable hydraulic oil. Engine oil should be Cat DEO or DEO-ULS (SAE 15W-40 or 10W-30). Coolant should be a high-quality ethylene glycol-based product, such as Fleet Charge Coolant. Avoid mixing different oil brands to prevent chemical reactions that cause sludge. Cross-contamination should be kept below 10 percent.

What should you check when buying a used D6H?

Verify the serial number prefix to determine the model year, engine series, and configuration (e.g., 4YF, 6FC, 5HF). Check for track frame cracks and previous weld repairs. Inspect the equalizer bar for excessive play. Verify the condition of the idler wheels and track pads. Test the transmission for overheating and check the cooler for clogs. Ensure the differential steer operates smoothly and that all gauges are functional. Be cautious of high-hour units with unknown maintenance histories; a dealer survey is recommended. Have your dealer verify the machine's specific configuration and serial number details before purchase.

Compiled from owner and technician discussions across the industry — experiences vary by serial range and machine history.

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