Caterpillartrack-type tractor

Caterpillar D7G

Maintenance schedule, common problems & OEM parts breakdown

The Caterpillar D7G is a mid-size track-type tractor (crawler dozer) built from 1974 into 1986 for civilian production, with military-contract units following into 1987. It sits in the D7 lineage between the D7F it replaced and the D7H that replaced it. Base/Series 1 machines run the Cat 3306 turbocharged diesel rated 165 kW/215 hp gross and 149 kW/200 hp net; later Series 2 production moved to the 3306 DITA (direct-injection, turbocharged, aftercooled), rated around 150 kW/202 hp net with a maximum flywheel rating near 164 kW/220 hp. Operating weight is configuration-dependent: a standard-gauge dozer-equipped machine runs close to 20.6 t (45,400 lb); the Low Ground Pressure (LGP) version, on a widened track gauge, runs heavier at roughly 23.6 t (52,100 lb); and the direct-drive SA (swamp/special application) variant, built for soft-ground work, is lighter at about 18.5 t (40,700 lb) despite its own wide gauge. Caterpillar paired Standard and LGP configurations with a planetary powershift transmission (torque converter and torque divider, three speeds forward and reverse) and offered the SA variant with a direct-drive gearbox instead, along with clutch-brake steering standard across the line.

Running changes between Series 1 and Series 2 were incremental rather than a redesign: the same 3306 block carried through, with the DITA aftercooled update raising output, plus smaller shifts in standard shoe width, hydraulic tank size, and second-gear travel speed. The mechanical, pre-electronic architecture (clutch-brake steering, powershift or direct-drive gearing, manually adjusted linkages) stayed constant throughout the run. Caterpillar drew the line under the D7G in the mid-1980s with the D7H, the first D7 built on an elevated-drive-sprocket undercarriage, a structural change that carried into every D-series dozer that followed and is the clearest split between this generation and the next. In the used and parts market the D7G remains common today because of its long production run, the sheer number built, and a driveline that any competent diesel shop can rebuild without factory diagnostic tools. Undercarriage condition drives most of its resale value, and worn examples are routinely kept working on remanufactured track components and reconditioned final drives, transmissions, and engines rather than scrapped.

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 D7G specifications

Engine

Engine model (D7G, base/Series 1)	Cat 3306 turbocharged diesel, inline 6-cylinder, four-stroke, direct injection
Engine model (D7G Series 2)	Cat 3306 DITA (direct-injection, turbocharged, aftercooled), inline 6-cylinder diesel
Gross power (Series 1)	165 kW / 215 hp at 2000 rpm
Net power (Series 1)	149 kW / 200 hp at 2000 rpm
Net power (Series 2)	150 kW / 202 hp at 2000 rpm, reads the same under Caterpillar, ISO 9249, SAE J1349 and EU 80/1269 ratings
Maximum flywheel power (Series 2)	164 kW / 220 hp
Bore x stroke	121 mm x 152 mm (4.75 in x 6.0 in)
Displacement	10.5 L (approx. 638-641 cu in, rounding varies by source)
D7G SA (swamp/special application) power	186 kW / 249.5 hp gross - higher output than the standard tractor to offset its direct-drive powertrain and wider gauge
Altitude derating	Rated power held without derating to roughly 2300 m (7500 ft); Series 2 literature cites capability to 4100 m (13,450 ft)
Emissions certification	Pre-emissions-regulation mechanically governed diesel; no exhaust aftertreatment fitted

Weights

Operating weight, standard w/ 7S straight blade & ROPS canopy (Series 1)	20,600 kg (45,370 lb) - includes lubricants, coolant, full fuel tank, hydraulic controls, blade and operator
Operating weight, standard w/ 7A angle blade (Series 1)	approx. 19,660-20,094 kg (43,300-44,300 lb), depending on whether ROPS canopy is included in the published figure
Operating weight, standard w/ 7S blade (Series 2)	20,580 kg (45,381 lb) - includes lubricants, coolant, two-valve hydraulics, 560 mm (22 in) shoes, non-ROPS cab, air conditioner, full fuel tank and operator
Shipping weight (Series 1)	15,380 kg (33,900 lb) bare; 16,170 kg (35,620 lb) with ROPS canopy added
Shipping weight (Series 2)	15,650 kg (34,510 lb)
Operating weight, LGP configuration	approx. 23,630 kg (52,095 lb) - treat as approximate; no factory specalog covering this configuration could be cross-checked
Operating weight, SA (swamp/special application)	approx. 18,460 kg (40,702 lb) - lighter than the standard tractor despite its wider swamp-track gauge

Dimensions

Track gauge, standard	1980-1981 mm (6 ft 6 in / 78.0 in)
Width over standard tracks	2560-2620 mm (8 ft 5 in to 8 ft 7 in), varies with shoe width fitted
Length of track on ground	2720 mm (8 ft 11 in / 107 in)
Basic tractor length, no attachment	4190-4198 mm (approx. 13 ft 9 in)
Length with 7S straight blade	5283 mm (17 ft 4 in)
Length with 7A angle blade	5486 mm (18 ft 0 in)
Length with drawbar	4521 mm (14 ft 10 in)
Length with ripper, tip on ground	4572 mm (15 ft 0 in)
Length with winch	5232 mm (17 ft 2 in)
Height to top of ROPS canopy	3250 mm (10 ft 8 in)
Height to top of cab, non-ROPS (Series 2)	3294 mm (129.7 in)
Ground clearance	347-349 mm (13.7 in / 1.14 ft), per SAE J894
Standard track shoe width	508-560 mm (20-22 in) depending on series/configuration; optional widths from 510-610 mm (20-24 in) offered
LGP track shoe width	860 mm (33.9 in)
LGP track gauge	approx. 2180-2235 mm (7 ft 2 in to 7 ft 4 in), widened for a low-ground-pressure footprint
LGP length with blade	approx. 5690 mm (18 ft 8 in)
SA (swamp application) track gauge	1981 mm (78 in) - standard gauge retained; a wider shoe and lighter chassis were used instead to get the swamp footprint

Performance

Transmission, standard and LGP	Planetary powershift, single-stage torque converter with an output torque divider, three speeds forward and three reverse
Transmission, SA (swamp/special application)	Direct drive, six speeds forward and four reverse - used instead of powershift for extra crawl control in soft-ground work
Travel speed, forward gears (Series 1)	2.3 / 4.0 / 6.2 mph (3.7 / 6.4 / 10.0 km/h)
Travel speed, reverse gears (Series 1)	2.8 / 4.9 / 7.4 mph (4.5 / 7.9 / 11.9 km/h)
Travel speed, forward gears (Series 2)	2.3 / 4.3 / 6.2 mph (3.9 / 6.9 / 9.9 km/h)
Travel speed, reverse gears (Series 2)	2.8 / 5.2 / 7.9 mph (4.5 / 8.4 / 12.7 km/h)
Travel speed, SA (direct drive)	max forward 5.1 mph (8.2 km/h), max reverse 4.8 mph (7.7 km/h) - slower top end than the standard powershift tractor due to swamp-application gearing
Ground pressure, standard configuration	roughly 10.3-10.6 psi (71-73 kPa), varies by series and shoe width fitted
Ground pressure, LGP configuration	not published in the technical literature reviewed for this model; a wide-track LGP setup is meant to read well below the standard-track figure - confirm with your dealer for an exact rating
Drawbar pull	factory literature publishes a calculated drawbar-pull-versus-travel-speed curve for each gear rather than a single peak figure; pull is highest at crawl speed in first gear and tapers off as travel speed rises through the range
Gradeability	not published as a stated maximum-grade figure in the technical literature reviewed for this model
Hydraulic pump output	227 L/min (60 gpm) at 2080 rpm and 6895 kPa (1000 psi)
Tilt cylinder flow	91 L/min (24 gpm)
Hydraulic relief valve settings	blade circuit 15,513 kPa (2250 psi); ripper circuit 15,513 kPa (2250 psi); tilt cylinder circuit 16,892 kPa (2450 psi)

Blades

7S straight blade capacity	4.2 m3 (5.5 yd3)
7S straight blade dimensions	width 3660 mm (144 in), height 1270 mm (50 in), digging depth 447 mm (17.6 in), maximum tilt 720 mm (28.4 in)
7S blade weight, without hydraulics	3475 kg (7660 lb)
7A angle blade capacity	2.9 m3 (3.8 yd3)
7A angle blade dimensions	width 4270 mm (168 in), height 970 mm (38 in), digging depth 480 mm (18.9 in), maximum tilt 300 mm (11.8 in)
7A blade weight, without hydraulics	3110 kg (6850 lb)
7SU semi-U blade capacity (Series 2)	5.75 m3 (7.53 yd3) - documented for Series 2 literature; base D7G Series 1 material reviewed lists only the S and A blades
LGP blade width	approx. 4.17-4.18 m (13.7 ft); blade profile not specified in the source
Ripper, factory fixed-parallelogram option	multi-shank beam, overall beam width 2210 mm (87 in), maximum lift height 490 mm (19 in), maximum rip depth 510 mm (20 in)

Service capacities summary

Fuel tank	415-435 L (110-115 gal), depending on series/printing
Cooling system	45.4 L (approx. 12 gal)
Engine crankcase, with filter	27-27.4 L (7.25-7.3 gal)
Final drive, each side	34-34.1 L (9.0 gal)
Hydraulic tank	91-102 L (24-27 gal), varies by series
Powershift transmission, bevel gear, steering clutch housings and torque converter	70 L (18.5 gal)
SA (swamp/special application) fuel tank	approx. 587 L (155 gal) - a larger tank fitted for extended remote-site operation

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

D7G fluids & capacities

System	Capacity	Recommended fluid
Engine crankcase (with filter)	27 - 27.4 L (7.25 - 7.3 US gal)	Cat Diesel Engine Oil (DEO). Viscosity graded by ambient temperature per the Cat OMM chart - SAE 10W in cold climates up to SAE 40 in hot climates, matched to the D7G's Cat 3306 DITA (direct-injection, turbocharged, aftercooled) diesel.
Cooling system	45.4 L (approx. 12 US gal)	Cat heavy-duty coolant/antifreeze with corrosion inhibitor, mixed with water per the OMM's freeze-protection table. Conventional SCA-treated coolant on earlier production; Cat Extended Life Coolant (ELC) referenced on later Series II production.
Fuel tank	435 L (115 US gal) on standard-production D7G; 415 L (110 US gal) cited for Series II - varies by configuration/series	No. 2-D diesel fuel (Cat fuel spec).
Powershift transmission, bevel gear and steering clutch compartments, torque converter	70 L (18.5 US gal) total - the OMM lists this as one shared/connected oil system rather than separate compartment fills	Cat TDTO (Transmission/Drive Train Oil). Viscosity selected by ambient temperature per the OMM chart - SAE 10W, 30W, or 50W.
Final drives (each side)	34 - 34.1 L (9.0 US gal) per side	Cat TDTO, generally a heavier grade than the transmission fill (SAE 30W/50W range), selected by ambient temperature per the OMM chart.
Hydraulic system/tank (blade, ripper, tilt implement circuit)	91 L (24 US gal) on standard-production D7G; 102 L (27 US gal) cited for Series II - varies by configuration/series	Cat TDTO-type oil shared with the powertrain fill, consistent with oil-commonality practice on Cat track-type tractors of this era. Confirm against the OMM for your serial prefix, as later production can call for a dedicated Cat hydraulic oil instead.
Pivot shaft	Not documented as a separate refill capacity in the sources reviewed	Not separately specified. On this machine class the pivot/equalizer compartment, where oil-lubricated, typically runs the same TDTO-spec oil as the final drives - verify against the OMM for your serial range.
Grease (track rollers, idlers, chassis and pin points)	Grease-gun applied via fittings; not capacity-rated	Cat multipurpose-type chassis grease, NLGI 2 for normal climates, stepping down to NLGI 1 or 0 in cold climates per Cat's general grease-selection guidance. Exact grade/brand name not confirmed in the specific D7G OMM excerpts reviewed.

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

Caterpillar D7G maintenance schedule

Service interval	Tasks
Every 50 h	Check engine oil and coolant levels before starting, with the engine cold and off. Drain water and sediment from the fuel tank and primary fuel filter/water separator. Walk-check track tension, shoes, and sprockets for damage; look for fluid leaks at the final drives and the transmission/steering-clutch compartment. Clean the radiator core and screen of debris and check the air cleaner service indicator. Grease blade lift/tilt pivots and steering-clutch/brake linkage points. Check battery condition, lights, gauges, and the ROPS/canopy structure before operating.
Every 250 h	Change engine oil and filter; pull an oil sample for analysis. Check the powershift/bevel-gear/steering-clutch compartment oil level. Inspect and adjust fan belt tension. Lubricate track roller frame and equalizer bar pivot points. Check battery electrolyte level and terminal condition. Inspect ripper shank and tip wear, if equipped.
Every 500 h	Change oil in the shared powershift/bevel-gear/steering-clutch/torque-converter compartment; pull a sample. Change final drive oil on each side and check the drain for metal. Replace primary and secondary fuel filters. Check hydraulic tank oil level and inspect the suction screen. Inspect and adjust steering clutch and brake linkage travel. Sample coolant and check corrosion-inhibitor concentration.
Every 1,000 h	Change hydraulic tank oil and filter. Check and adjust engine valve lash. Inspect the turbocharger for shaft play and boost or exhaust leaks; on DITA engines check aftercooler flow. Re-torque track shoe bolts and inspect roller and idler seals for weeping. Test alternator, starter, and glow-plug circuit output. Check steering clutch and brake disc wear through the inspection cover.
Every 2,000 h	Change engine coolant or renew the corrosion inhibitor based on the coolant sample trend. Inspect powershift transmission clutch packs and the torque divider for wear via oil sampling and pressure checks. Inspect final drive gearsets and bearings for pitting or wear. Inspect steering clutch and brake disc thickness and plan adjustment or replacement. Check ROPS/canopy mounts and main frame welds for cracks. Recheck hydraulic relief valve settings on the blade, tilt, and ripper circuits.
Every 4,000 h	Evaluate undercarriage wear (chain pitch, roller and idler flanges, sprocket teeth) against factory wear limits and plan renewal. Inspect final drives for gear-tooth wear or chipping and rebuild as needed. Assess steering clutch and brake pack condition for a mid-life rebuild. Check main frame and pivot/trunnion wear at a partial teardown.
Every 8,000 h	Plan an engine inframe or full overhaul (reringing/reboring, injector and turbocharger reconditioning) once compression or oil-analysis trends call for it. Rebuild or exchange the powershift transmission and torque divider once clutch-pack wear exceeds trended limits. Replace or rebuild the complete undercarriage (chain, rollers, idlers, sprockets) once past factory wear limits. Rebuild steering clutches, brakes, and final drives together, since they share the same compartment oil and wear as a group. Recondition or replace hydraulic cylinders and the control valve if internal bypass or spool wear has developed.

Servicing the D7G beyond the schedule

Predictive Maintenance & Fluid Analysis

Sample oil from the engine, the shared powershift/steering-clutch compartment, and each final drive on a regular interval; the D7G's mechanical driveline shows wear through metals in these samples long before a symptom appears. On DITA-engined Series 2 units, watch coolant quality: scale from poor coolant restricts the water-to-air aftercooler and shows up as lost power and rising exhaust temperature before the engine is at fault. Track undercarriage wear gauges regularly, since chain, roller, and sprocket wear drives most of this machine's rebuild cost.

Corrective & Common Repairs

Power loss under load with normal engine revs points first at transmission/converter oil level, screen condition, and test-port pressure before the converter is blamed; true internal slippage needs an overhaul, not an adjustment. A machine that won't move in gear with the engine and blade working fine points at the transmission itself. Track popping at the drive sprocket usually means a new sprocket was fitted to a stretched, unmeasured chain. Suction-side fuel air leaks and weeping injector seals after long idle are common on high-hour 3306s.

Overhaul & Rebuild Points

A D7G overhaul centers on the 3306: reringing/reboring, injector reconditioning, and, on DITA units, aftercooler cleaning once compression or exhaust-temperature trends fall off. The powershift transmission's torque-divider and clutch packs, steering clutch, and brake discs form the next wear group and typically get rebuilt together since they share one oil compartment. Final drive gearsets and bearings should be checked whenever that compartment is opened. Complete undercarriage renewal (chain, rollers, idlers, sprockets) is the largest rebuild expense and should be planned from wear-gauge readings, not a fixed hour figure.

Seasonal & Environment Servicing

Below about 2°C (35°F), this mechanically governed engine normally needs its ether starting aid and warmed glow plugs to fire; a long crank with no ether response points at the glow-plug circuit, not the engine. Drain fuel-tank and filter water more often as seasonal condensation increases, and check coolant freeze protection before winter. In hot, dusty ground, service the air cleaner and clean the radiator core more often to protect the turbocharged 3306 from overheating. LGP machines in soft or wet ground need more frequent track and roller-frame checks.

D7G common service parts

Part number	Part	Notes
1D-4540	Bolt,Machine Fuel Filter Mounting	Fuel system service	Check fitment →
1H-5514	Bolt,Machine Engine Oil Filter Assembly	Lubrication service	Check fitment →
8M-3182	Spring,Helical,Comp Engine Oil Filter Assembly	Lubrication service	Check fitment →
2P-2537	Stud Engine Oil Filter	Lubrication service	Check fitment →
8T-6765	Plug-Pipe	Scheduled service item	Check fitment →

Always confirm against your machine's serial number — cross-check any part in Heavy Parts AI before ordering.

D7G fault codes & troubleshooting

Code	Meaning	Likely cause	What to do
ENGINE OIL PRESSURE warning lamp + audible alarm	Engine lubrication oil pressure has dropped below the safe minimum monitored by the panel's pressure switch.	Low oil level, worn oil pump, clogged oil filter or suction screen, or a failed pressure sending unit.	Stop the engine right away, check oil level and filter condition, then confirm actual pressure with a mechanical test gauge at the block before restarting.
COOLANT TEMPERATURE warning lamp	Engine coolant temperature has moved above the normal operating range shown by the panel's temperature sender.	Low coolant level, a plugged radiator core, a slipping or failed fan drive, a stuck thermostat, or a bad temperature sending unit.	Idle the engine down, check coolant level and radiator restriction once it is safe to open the cap, and inspect the fan belt/drive and thermostat before returning to work.
ALTERNATOR / CHARGING warning lamp	The battery is not receiving charge current from the alternator, as tracked by the charging circuit.	A worn or broken alternator belt, a failed alternator, a bad voltage regulator, or a loose or corroded battery/ground connection.	Check belt tension and battery connections first; if the lamp stays lit, test alternator output and regulator with a multimeter.
TRANSMISSION / TORQUE CONVERTER OIL TEMPERATURE warning lamp	Torque converter and transmission oil temperature has exceeded the safe operating range.	Restricted or plugged transmission oil cooler lines, a weak scavenge pump, converter wear causing excess slippage, low oil level, or air pulled in at a suction line.	Reduce load and let the machine idle to cool, check oil level and cooler line flow, then confirm the reading with a mechanical temperature gauge before resuming heavy work.
AIR CLEANER RESTRICTION indicator	Vacuum-actuated service indicator on the air intake shows restriction has reached the point where the filter needs attention.	A dirty or clogged primary air filter element, a damaged element, or a loose intake hose connection.	Inspect and clean or replace the primary air filter element (and secondary if contaminated), reset the indicator, and check hose clamps and seals.
TRANSMISSION OIL FILTER BYPASS indicator	Pop-up mechanical button on the transmission oil filter head shows the bypass valve opened because the element restricted oil flow.	A clogged transmission oil filter element, oil that is too cold or thickened, or a filter left in service past its interval.	Replace the transmission oil filter element, reset the indicator button, and check oil condition and change interval.

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

D7G attachments & work tools

Blades

D7G blade line covers straight (S), semi-universal (SU) and angling (A) types. Straight blade capacity runs about 4.2 m3 (5.5 yd3); semi-universal, offered as a custom option, about 5.75 m3 (7.53 yd3); angling about 2.9 m3 (3.8 yd3) with side-cast angling to roughly 25 degrees either direction. S and SU blades come with a hydraulic tilt cylinder; the A blade tilts by angling instead. No VPAT blade was ever cataloged for the D7G/D7E generation - that feature arrived later on the T-series medium dozers. The LGP undercarriage variant runs wider tracks and a wider blade for lower ground pressure; exact LGP blade width varies by source, verify against the build sheet for a given unit.

Rippers

Main optional rear ripper for this class is a fixed parallelogram multi-shank unit. A multi-shank ripper assembly sized for the D7G runs roughly 2.5-2.9 t (5,500-6,400 lb) complete. Single-shank rippers were also fitted in this class for maximum-penetration work in hard or rocky ground, trading ripping width for concentrated point load versus the multi-shank frame - choice is job-condition dependent, not a fixed factory default.

Winches

D7G most commonly ran a rear PTO/cable-control drum winch built specifically for this chassis (and the 572G pipelayer), with non-free-spool operation and brake-off/drive-away control - mechanically driven off the transmission PTO rather than the hydraulic system. Later high-drive-based PTO winch lines built for D7H/D7R and D8-class dozers are not a direct fit to the D7G's low-drive undercarriage; treat cross-model winch listings with caution and match to the specific chassis.

Drawbars/counterweights

Rear end of the D7G takes one of: drawbar (towing), counterweight casting, ripper, or winch - these share the same rear mounting location and are mutually exclusive on one machine. A rear ripper or winch supplies its own counterbalancing mass against the front blade load, so a separate counterweight is only needed when the rear end is left bare (drawbar-only or no rear attachment).

Cab/ROPS guarding

Standard cab/canopy is an integrated ROPS structure with improved side visibility. No factory-cataloged forestry or waste/landfill guarding package is documented specifically under the D7G nameplate; operators in land-clearing and landfill work commonly add bolt-on brush screens over the cab glass plus limb-riser sweeps running from the blade up over the cab roof, deflecting branches and debris around the operator station and engine compartment rather than through it.

Hydraulic arrangement

Blade lift, and tilt on S/SU blades, run off the tractor's own hydraulic pump circuit independent of the ripper controls; non-power-tilt setups instead use a mechanically adjustable brace. The rear multi-shank ripper's parallelogram linkage runs on its own hydraulic lift and pitch cylinders, so blade and ripper operate without cross-interference. The PTO winch is transmission-driven, not hydraulic, so winching adds no heat load to the dozer's hydraulic system.

All D7G assemblies by section

Every catalogued assembly group for the Caterpillar D7G. Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.

Air Inlet And Exhaust System

219-1911 Turbocharger Gp

11***16	Housing (Turbine)	1
11***17	Cover (Compressor)	1
21***09	Cartridge Group-Turbocharger	1
21***11	Turbocharger Group	1

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Basic Engine

9n-5760 Damper Gp

1W***78	Spring; (35.7mm Long)	2
1W***79	Spring; (54.6mm Long)	2
4B***73	Screw-Machine; (10-24x0.5-In)	2
6F***18	Packing,Preformed Part Of Kit P/N 5r***28	1

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284-7810 Kit-Hardware

03***19	Bolt; --To Bearing Ret. At Lower Front Shaft Bore	4
03***57	Bolt; --To Reverse Shaft Bearing Retainer & Forward Shaft Bearing Retainer	4
0L***43	Bolt 63.5 mm (3/8" X 2 1/2" -Cover Assembly To Fender	1
0L***51	Bolt Starting Engine Fuel Tank Bracket To Diesel Intake Manifold	1

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Cooling System

4w-5363 Core Gp-Oil Cooler

4W***63	Core Group-Oil Cooler; -Transmission	1
6V***49	Seal-O-Ring (Id=11.89mm); (11.89-mm Id)	1
9S***91	Plug,Machine Thread Fuel Injection Pump	1

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Engine Arrangement

284-3284 Conversion Ar-Engine

0R***14	Rod As-Connecting	1
0R***43	Cylinder Pack Group	6
0R***91	Nozzle As-Fuel Valve	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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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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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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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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Service Equipment And Supplies

284-3295 Kit-Engine Parts

10***37	Bracket Assem.	1
10***33	Tube As-Control	1
11***28	Elbow; (90-Deg)	1
12***88	Housing-Aftercooler	1

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D7G serial number reference

The D7G PIN/serial plate is mounted high on the left-hand frame rail toward the rear of the tractor, near the final drive, and can be hard to see or hidden behind a rear ripper or drawbar on ripper-equipped units. The plate shows the model designation followed by the serial number, a 2-3 character prefix (letters and digits) plus a sequential unit number. Match the full prefix, not just the trailing digits, when looking up the correct parts book or service manual, since the prefix is what identifies the production break.

Prefix	Identifies	Notes
35N	D7G track-type tractor, Direct Drive powertrain, early production run	Direct-drive tractors from near the start of D7G output; factory literature lists this as an early Direct Drive break. D7G was introduced in 1974, so this prefix sits early in the run. Cat 3306 diesel. Clutch-brake steering, standard for the D7G line.
3ZD	D7G track-type tractor, late production run, military-contract parts book documented	A dedicated parts book for this prefix is dated 1987 and is a military edition, consistent with the armored D7G used by U.S. Army engineer units. Places this break at or just after the end of civilian D7G production (D7G was succeeded by the D7H in 1986). Cat 3306 diesel, clutch-brake steering.
44W	D7G track-type tractor, mid-production run	Covered under the same factory service manual as the other core D7G breaks. Testing-and-adjusting literature for the power-shift transmission cites an early span for this prefix; a separate parts-catalog edition also exists. Cat 3306 diesel, clutch-brake steering. Exact model year not documented in available listings.
64V	D7G track-type tractor, mid-to-late production run	Covered under the same factory service manual as the other core D7G breaks. Cat 3306 diesel, clutch-brake steering. Exact model year not documented in available listings.
65V	D7G track-type tractor, mid-to-late production run	Covered under the same factory service manual as the other core D7G breaks; a parts manual and separate testing-and-adjusting literature for the power-shift transmission both document this break across a long production run. Cat 3306 diesel, clutch-brake steering. Exact model year not documented in available listings.
91V	D7G track-type tractor, Direct Drive powertrain	Documented specifically for the direct-drive powertrain in wiring-diagram and operation-and-maintenance literature, with the exact configuration confirmed by a dedicated wiring-diagram cross-reference. Cat 3306 diesel, clutch-brake steering.
92V	D7G track-type tractor, Powershift powertrain	Largest documented D7G break, with sequential sub-ranges showing a long production run under one prefix. Wiring-diagram literature confirms the early span specifically as the powershift (torque-divider power train) configuration rather than direct drive. Cat 3306 diesel, clutch-brake steering.
4YB	D7G track-type tractor, late production run	Parts-catalog listings date this break to around 1983. Cat 3306 diesel, clutch-brake steering.
3GF	D7G track-type tractor, Powershift powertrain	Documented for the torque-converter/power-train section and has a dedicated service manual, confirmed by a separate torque-converter/power-train listing. Powershift-equipped. Cat 3306 diesel, clutch-brake steering.
62Z	D7G track-type tractor, Powershift powertrain (thin documentation, confirm with dealer)	Cited as a serial break inside a Powershift-specific parts book that also spans the 92V, 2GA, and 3N breaks, rather than having its own dedicated manual. Confirm with a dealer before relying on it.
2GA	D7G track-type tractor, Powershift powertrain (thin documentation, confirm with dealer)	Cited as a serial break inside the same Powershift parts book covering 92V, 62Z, and 3N, rather than having its own dedicated manual. Confirm with a dealer before relying on it.
3N	D7G track-type tractor, Powershift powertrain (thin documentation, confirm with dealer)	Cited as a serial break running from partway through the range up to the last unit built under it, inside the same Powershift parts book covering 92V, 62Z, and 2GA. The prefix is a two-character letter-number format matching the other breaks in this book. Confirm the exact range with a dealer before relying on it.

Frequently asked questions

What engine does the Caterpillar D7G use?

The D7G runs Caterpillar's own 3306 inline six-cylinder diesel. Base/Series 1 production used the turbocharged version, rated 165 kW/215 hp gross and 149 kW/200 hp net. Later Series 2 production moved to the 3306 DITA (turbocharged, aftercooled), rated around 150 kW/202 hp net with a maximum flywheel rating near 164 kW/220 hp. The direct-drive SA (swamp/special application) variant used a higher-output rating near 186 kW/249.5 hp gross.

What is the operating weight of the Caterpillar D7G?

Operating weight depends on configuration. A standard-gauge dozer-equipped D7G runs close to 20.6 t (45,400 lb). The wide-track LGP version runs heavier, around 23.6 t (52,100 lb). The direct-drive SA swamp variant is lighter, around 18.5 t (40,700 lb), despite its own wide gauge.

What replaced the Caterpillar D7G?

Caterpillar replaced the D7G with the D7H in the mid-1980s. The D7H was the first D7 built on Caterpillar's elevated-drive-sprocket undercarriage, a design that carried forward into later D-series dozers and marks the clearest break from the D7G generation.

What D7G owners discuss

What does a worn torque converter or power-shift problem look like on the D7G, and what should be ruled out first?

Power loss under load — engine revs stay normal but the tractor bogs down pushing a full blade, especially on a grade — points first at transmission/converter oil level, screen condition, and pump pressure at the test ports before the converter itself is blamed. Low oil, a plugged screen, or a stuck priority valve can mimic converter wear. True slippage traced to worn internal clearances (stator/turbine) has no field adjustment; only an overhaul restores performance. A separate symptom — engine runs fine, blade works fine, but the machine won't move in gear — points at the transmission itself, not the engine or converter.

Why do experienced owners warn against fitting new sprocket segments on an old, stretched track chain?

Chain pitch stretches as it wears. A new sprocket is cut to new-chain pitch, so pairing it with a stretched chain misaligns the teeth against the bushings — this shows up as a popping or jumping noise at the drive sprocket and speeds up wear on both parts. Measure chain pitch wear before deciding whether to renew sprocket, chain, or both together. Wear is rarely even side to side: a dozer worked repeatedly downhill on one track wears that side faster, so compare left and right before condemning a component as simply worn out.

Does an older D7G have the same engine as a later "Series II" unit?

Not necessarily. The original D7G, introduced in the mid-1970s, used the Cat 3306 turbocharged diesel. The later D7G Series II moved to the 3306 DITA — direct-injection, turbocharged, aftercooled — rated near 150 kW (202 hp) net flywheel power at 2,000 rpm, noticeably stronger than the earlier turbo-only engine. On DITA-equipped units, mineral scale from poor coolant quality is a known cause of restricted flow through the water-to-air aftercooler, showing up as reduced power and higher exhaust temperature well before the engine itself is at fault. Confirm the engine variant fitted to a specific machine from its rating plate or serial prefix rather than assuming from the model name alone.

What fuel-system quirks are common on high-hour D7G engines?

A gradual power loss after an hour or two of work, ending in sputtering and stall, is commonly traced to a suction-side air leak or restriction starving the injection pump — check fuel lines, the lift pump, and filter seals for air ingress even when the tank isn't empty. Injectors running hot and weeping at the top seal after a machine sits idle for months and gets restarted is another recurring complaint, pointing at injector sealing rings and precombustion chambers rather than the injection pump. These are wear and seal issues typical of an aging mechanical fuel system — the D7G has no electronic engine controls to fault instead.

The D7G won't start in cold weather even with decent compression. What's normal and what isn't?

On these mechanically governed, pre-electronic Cat dozers, needing the ether starting aid below roughly 2°C (35°F) is normal, not a sign of a failing engine. What isn't normal is a long crank with no sign of firing even with ether and warmed glow plugs — that points at the glow plug circuit: a loose connection, a failed glow plug, or a bad relay. Needing several minutes of glow-plug heat before cranking suggests weak plugs or resistance in that wiring, not a fuel problem. Gauges on the D7G (oil pressure, water temperature, charge) are simple mechanical or single-wire sender types; an erratic or dead gauge is usually a bad sender or a corroded connection at the cluster, not a harness fault.

The blade and tilt cylinders stopped responding, no visible leaks, oil level normal — where do owners look?

With no external leak and correct oil level, suspect internal bypass in a lift cylinder (worn piston seal passing oil internally under load) or a stuck or worn valve spool/linkage inside the control valve, rather than the pump. Run the system, then feel each cylinder body after a few minutes of operation — one noticeably warmer than the other points to that cylinder bypassing internally. Also check that the control-valve linkage hasn't dropped a pin inside the housing, which leaves a lever moving freely with no effect on the valve. Loss of blade control is a safety issue if the blade is raised or loaded when it happens — have your dealer or a qualified tech verify the diagnosis and any cylinder or valve repair before returning the machine to work.

What should I check before buying a used D7G?

Start with the undercarriage — it's a large share of the machine's value and the larger share of lifetime repair cost. Check roller and idler flange wear, sprocket tooth condition against chain pitch, and compare left-side wear to right-side (uneven wear often means the machine worked slopes in one direction). Start the engine cold if you can and watch for blow-by at the oil fill tube, then run the transmission through forward and reverse and note any hesitation on the shift — this can mean anything from normal wear to a costly transmission or converter issue. Test-drive it and confirm it tracks straight; pulling to one side can be a simple brake-band adjustment or a sign of a worn steering clutch. Inspect the blade, cutting edge, and trunnion pins for wear, and look for welds or plate lines that indicate prior repair. Ask for maintenance and application records — sandy-soil work wears differently than rock or quarry work. Because steering clutches and brakes are safety-critical and hard to fully judge on a short test drive, have your dealer or a qualified tech verify their condition before you put the machine to work.

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

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