Caterpillarwheel tractor-scraperwheel tractor
Caterpillar 637D
Maintenance schedule, common problems & OEM parts breakdown
The Caterpillar 637D is a heavy-duty wheel tractor-scraper designed for large-scale earthmoving, mining, and agricultural applications. This machine belongs to the 637 series lineage, which originated from the 631C tractor unit. The 637D configuration features a 3306 engine powering the tractor unit. It is characterized by its significant dimensions: overall length of 48.56 ft (14.80 m), overall width of 13 ft (3.96 m), and overall height of 13.69 ft (4.17 m). The unit operates with a wheelbase of 28.68 ft (8.74 m).
The 637D represents a specific evolutionary step in the 637 family, positioned between earlier models and later iterations like the 637E, 637G, and the modern 637K flagship. In today's used equipment market, the 637D remains a vital asset for operators requiring high-capacity open bowl scrapers. Its value is driven by the availability of robust components and its proven ability to haul, dig, and level topsoil in demanding environments. Maintenance of the powertrain and scraper unit is critical for preserving operational efficiency and resale value.
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 637D specifications
Engine
| Tractor Engine Model | Caterpillar 3408 |
| Tractor Net Power | 450 hp |
| Tractor Displacement | 1098.5 cu in |
| Scraper Engine Model | Caterpillar 3306 |
| Scraper Net Power | 255 hp |
| Scraper Displacement | 640.8 cu in |
Weights
| Total Operating Weight (Empty) | 106,174.7 lb |
| Total Operating Weight (Loaded) | 181,131.9 lb |
| Front Axle Weight (Empty) | 64,767.5 lb |
| Rear Axle Weight (Empty) | 41,407.3 lb |
| Front Axle Weight (Loaded) | 90,566 lb |
| Rear Axle Weight (Loaded) | 90,566 lb |
| Rated Payload | 74,957.2 lb |
Dimensions
| Overall Length | 48.56 ft |
| Overall Width | 13 ft |
| Overall Height | 13.69 ft |
| Wheelbase | 28.68 ft |
| Width of Cut | 11.5 ft |
| Max Depth of Cut | 19.1 in |
Performance
| Max Forward Speed | 31.7 mph |
| Number of Forward Gears | 8 |
| Heaped Bowl Capacity | 31 yd³ |
| Struck Bowl Capacity | 21.1 yd³ |
Service capacities (summary)
| Fuel Capacity | 370.7 gal |
| Engine Oil Specification | CAT DEO |
| Transmission Fluid Specification | CAT TDTO |
| Hydraulic Oil Specification | CAT HYDO Advanced |
Values vary by configuration, region, and serial range — confirm against your machine before planning transport or lifts.
637D fluids & capacities
| System | Capacity | Recommended fluid |
|---|---|---|
| Engine crankcase (with filter) | Not specified | CAT DEO or DEO-ULS; SAE 15W-40, SAE 10W-30, or SAE 0W-40 for cold weather |
| Cooling system | Not specified | Cat ELC (Extended Life Coolant) |
| Hydraulic system and tank | Not specified | Cat HYDO Advanced |
| Grease | Not specified | Varies by application: CAT Multipurpose Grease (low-load/low-speed), CAT Advanced 3Moly Grease (medium-load/medium-speed), or CAT Ultra 5Moly Grease (high-load/high-speed); use CAT Arctic Platinum Grease for cold-weather; use CAT Desert Gold Grease for hot-weather |
Capacities are refill values from factory literature — always fill to the dipstick/sight gauge, not the number.
Caterpillar 637D maintenance schedule
| Service interval | Tasks |
|---|---|
| Every 10 h |
|
| Every 250 h |
|
| Every 500 h |
|
| Every 1,000 h |
|
| Every 2,000 h |
|
Servicing the 637D beyond the schedule
Predictive Maintenance & Fluid Analysis
Utilize Caterpillar S.O.S Services to monitor engine oil, hydraulic fluid, coolant, and transmission oil. Analyze engine oil for wear metals like iron or copper and contaminants such as silicon from dirt ingestion. For the 637D, monitoring hydraulic oil particle counts and water content prevents pump and valve damage. Regular sampling during PM3 and PM4 intervals provides an early warning system to detect degradation before catastrophic component failure occurs.
Corrective & Common Repairs
Address frequent issues by monitoring hydraulic hose condition for cracks or abrasions that lead to leaks. Inspect the 3306 engine's valve mechanism cover and rocker arms if abnormal noise or oil loss is detected. Ensure all pins, bushings, and attachment points are lubricated to prevent seizure. If hydraulic performance drops, check for contamination in the return filters or air ingestion through the primary air filter element.
Overhaul & Rebuild Points
Plan major interventions around the 2,000-hour PM4 interval. Key rebuild focus areas include a full hydraulic oil change and transmission service. Evaluate the turbocharger for wear and perform comprehensive structural inspections of the chassis and scraper bowl. For high-hour machines, assess the condition of the 3306 engine components and prepare for potential major component evaluation or engine overhaul if wear metals in S.O.S reports exceed limits.
Seasonal & Environment Servicing
In dusty or quarry environments, shorten air filter inspection intervals to daily and replace them at 500 hours instead of the standard interval. Clean radiator and oil cooler fins daily to prevent overheating. For cold weather operations, use appropriate SAE 10W-30 engine oil for better starting capability. In high-load or hot climates, optimize hydraulic oil drain intervals and ensure the cooling system is fully serviced with fresh coolant.
637D common service parts
| Part number | Part | Notes | |
|---|---|---|---|
| 1R-0749 | Filter-Fuel | Fuel system service | Check fitment → |
| 1R-0716 | Filter As-Engine Oil | Lubrication service | Check fitment → |
| 8T-6765 | Plug-Pipe | Scheduled service item | Check fitment → |
| 9S-8752 | Nut-Full | Scheduled service item | Check fitment → |
Always confirm against your machine's serial number — cross-check any part in Heavy Parts AI before ordering.
637D fault codes & troubleshooting
| Code | Meaning | Likely cause | What to do |
|---|---|---|---|
| 110-0 | Engine Coolant Temperature — Above Normal | Low coolant level, thermostat failure | Inspect cooling system, refill coolant, test thermostat |
| 110-3 | Engine Coolant Temp Sensor — Voltage High | Open circuit or sensor failure | Check wiring; replace sensor if confirmed faulty |
| 174-3 | Engine Fuel Temperature — Voltage Above Normal | Open circuit in sensor wiring | Inspect harness and replace sensor if necessary |
| 190-8 | Engine Speed — Abnormal Frequency | Speed sensor air gap, sensor failure, or tone ring damage | Check sensor gap; test speed sensor and tone ring |
| 41-3 | 8-Volt DC Supply — Voltage Above Normal | Short to power on 8V reference circuit | Inspect sensors sharing the 8V supply and isolate fault |
| 41-4 | 8-Volt DC Supply — Voltage Below Normal | Short to ground on 8V reference circuit | Disconnect sensors one at a time to locate short |
| 2348-9 | SAE J1939 Data Link #2 — Abnormal Update Rate | CAN bus wiring damage or termination fault | Check CAN wiring and measure termination resistance |
Codes and remedies are general guidance for this model family — always confirm with diagnostic tooling and your dealer before major repairs.
637D attachments & work tools
Bowl/Scraper Attachments
Open bowl configurations are standard for this model. Typical capacities include a heaped capacity of 31 yd³ (23.7 m³) and a struck capacity of 21.1 yd³ (16.1 m³). The width of cut is 11.5 ft (3.5 m) with a maximum depth of cut of 19.1 in (48.5 cm).
Hitch and Coupling Systems
The machine utilizes an Advanced Cushion Hitch system. This configuration manages dampening rates to prevent endstroke events and reduce maintenance requirements.
Hydraulic and Operational Kits
Optional Cat Grade attachments include Sequence Assist and Load Assist technologies to assist operators. The tractor may be equipped with a hydraulic on-demand fan to assist in reducing fuel consumption.
Operator Cab and Guarding Options
Configurations vary by region and include both OROPS and enclosed Cab options. A powered access ladder system is available as an optional attachment for easier entry. Safety features may include a seat belt indicator providing visual and audible alerts.
All 637D assemblies by section
Every catalogued assembly group for the Caterpillar 637D. Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.
Air Inlet And Exhaust System
308-0896 Aftercooler Gp-Water
| 0L***43 | Bolt 63.5 mm (3/8" X 2 1/2" -Cover Assembly To Fender | 2 |
| 0S***71 | Screw,Cap,Hexagon; Tube Assembly To Turbocharger And Elbow Mounting | 14 |
| 0S***90 | Bolt; (3/8-16x2in)(Clip Thru Spacer To Bracket As) | 2 |
126-7290 Aftercooler Gp-Water
| 0L***43 | Bolt 63.5 mm (3/8" X 2 1/2" -Cover Assembly To Fender | 2 |
| 0S***71 | Screw,Cap,Hexagon; Tube Assembly To Turbocharger And Elbow Mounting | 14 |
| 0S***90 | Bolt; (3/8-16x2in)(Clip Thru Spacer To Bracket As) | 2 |
1w-1653 Cartridge Gp-Turbocharger
| 0S***16 | Screw,Cap,Hexagon H Receptacle Mtg; Bolt Brackets To Firewall Assembly | 4 |
| 12***63 | Wheel-Compressor | 1 |
| 1P***20 | Ring-Seal | 1 |
232-7438 Lines Gp-Air
| 0L***52 | Capscrew (3/8 - 16 Nc X 3 1/4 Gd8, Hex) | 3 |
| 0L***70 | Bolt (2-1/4") Filler Tube Assembly To Transfer Drive Case | 2 |
| 0S***71 | Screw,Cap,Hexagon; Tube Assembly To Turbocharger And Elbow Mounting | 8 |
166-0164 Manifold Gp-Exhaust
| 10***12 | Spacer; (11.13x19.05x53-mm Thk) | 16 |
| 12***52 | Gasket-Exhaust Manifold | 8 |
| 16***09 | Manifold-Exhaust | 2 |
253-4431 Muffler & Converter
| 1W***53 | Cartridge Group-Turbocharger | 1 |
| 25***31 | Muffler & Converter | 1 |
| 6N***85 | Housing-Turbine; (Turbine) | 1 |
1w-5580 Turbocharger Gp
| 1S***95 | Gasket-Turbocharger To Manifold; Gasket Turbocharger To Manifold | 1 |
| 1W***80 | Turbocharger Group | 2 |
| 2N***65 | Bolt-High Temperature; (3/8-16x1.75-In) | 4 |
127-9177 Turbocharger Gp
| 12***33 | Pedal | 2 |
| 12***34 | Plate As | 2 |
| 12***14 | Pin | 2 |
Basic Engine
7w-6245 Cover Gp-Flywheel Housing
| 0S***66 | Bolt-Pulley To Crankshaft Adapter | 3 |
| 0S***94 | Bolt (1 In. Long 3/8 In. Dia.); Plate Assembly To Support Assembly | 1 |
| 0S***19 | Bolt,Machine Gear Retaining Part Of Kit P/N 1w***46 | 1 |
4n-6842 Air Compressor Gp
| 0L***51 | Bolt Starting Engine Fuel Tank Bracket To Diesel Intake Manifold | 5 |
| 12***48 | Seal-Integral | 1 |
| 1F***58 | Nut-Full; (1/2-13-Thd)(Air Lines) | 3 |
4n-7378 Air Compressor Gp
| 0S***19 | Bolt,Machine Gear Retaining Part Of Kit P/N 1w***46 | 6 |
| 11***37 | Kit-Piston Ring; (Compressor 5 Ring) | 1 |
| 1W***03 | Plug | 2 |
284-7031 Air Compressor Gp
| 0L***51 | Bolt Starting Engine Fuel Tank Bracket To Diesel Intake Manifold | 5 |
| 12***48 | Seal-Integral | 1 |
| 1F***58 | Nut-Full; (1/2-13-Thd)(Air Lines) | 3 |
4n-1092 Balancer Gp
| 0L***51 | Bolt Starting Engine Fuel Tank Bracket To Diesel Intake Manifold | 4 |
| 1B***82 | Bolt (1.25 In. Long X .313 In. Dia.) | 1 |
| 1W***49 | Shaft-Balance Weight | 1 |
108-1547 Camshaft Gp
| 0S***09 | Bolt (3/4") Filler Tube Assembly To Transfer Drive Case | 2 |
| 10***74 | Gear-Camshaft Drive; (86-Teeth) | 1 |
| 10***47 | Camshaft Group | 1 |
4n-6866 Cover Gp-Cylinder Block
| 0S***94 | Bolt (1 In. Long 3/8 In. Dia.); Plate Assembly To Support Assembly | 12 |
| 23***37 | Seal-Integral | 1 |
| 23***71 | Seal-Integral | 1 |
126-0768 Cover Gp-Front Housing
| 0L***52 | Capscrew (3/8 - 16 Nc X 3 1/4 Gd8, Hex) | 6 |
| 0S***94 | Bolt (1 In. Long 3/8 In. Dia.); Plate Assembly To Support Assembly | 3 |
| 11***21 | Support-Housing; (Rh) | 1 |
4n-8159 Cover Gp-Oil Pan
| 0S***87 | Bolt-Bracket Assembly To Timing Gear | 2 |
| 0S***88 | Bolt,Machine; Hose Assembly Mounting,Hose Assembly To Transmission,And To Torque Converter | 2 |
| 10***72 | Seal-O-Ring; (40.64-mm Id) | 2 |
125-9246 Cover Gp-Valve Mechanism
| 10***88 | Base-Valve Mechanism Cover | 4 |
| 11***84 | Cover-Valve Mechanism | 1 |
| 11***15 | Cover As-Valve | 3 |
1w-5009 Crankshaft As
| 1W***09 | Crankshaft As | 1 |
| 4N***84 | Dowel; (.75 Long) | 1 |
| 7N***91 | Gear-Crankshaft; (80-Teeth) | 1 |
1w-5010 Crankshaft Gp
| 1W***09 | Crankshaft As | 1 |
| 1W***10 | Crankshaft Group; Crankshaft Group | 1 |
| 24***18 | Kit-Crankshaft Bearing | 0 |
110-3779 Cylinder Block As
| 11***20 | Seal-O-Ring; (Mid-Liner) | 8 |
| 11***79 | Cylinder Block As | 1 |
| 14***17 | Seal-O-Ring; (140.20mm Id) | 8 |
109-9009 Cylinder Block Gp
| 10***17 | Stud-Taperlock | 18 |
| 10***09 | Cylinder Block Group | 1 |
| 11***09 | Cylinder Block As | 1 |
143-0040 Cylinder Head As
| 14***40 | Cylinder Head As | 1 |
| 1W***83 | Insert-Valve Seat; (Exhaust)(Standard) | 8 |
| 3B***23 | Core Plug--Flywheel Housing Pinion Shaft Hole | 8 |
143-3614 Cylinder Head As
| 10***94 | Dowel | 2 |
| 14***40 | Cylinder Head As | 1 |
| 14***14 | Cylinder Head As | 1 |
107-7320 Cylinder Head Gp
| 10***20 | Cylinder Head Group | 1 |
| 12***21 | Valve-Exhaust | 8 |
| 12***22 | Valve-Inlet | 8 |
107-7319 Cylinder Head Gp
| 03***27 | Seal-O-Ring; (19.18mm Id) | 2 |
| 06***61 | Seal-O-Ring (Id=40.87mm) | 8 |
| 10***92 | Stud-Taperlock; (3/8-16x3.93in) | 16 |
4p-5893 Damper Gp
| 16***26 | Damper Assem. | 1 |
| 16***00 | Spacer; (131.57mmx163.6mmx8mm Thk) | 1 |
| 1A***03 | Bolt 12.07 cm(4.75 In.) Long | 6 |
9n-0725 Drive Gp-Accessory
| 5P***40 | Seal-O-Ring | 1 |
| 6B***83 | Nut,Plain,Hexagon Lever | 1 |
| 7N***22 | Gear-Compressor Drive; (46-Teeth) | 1 |
7w-4999 Flywheel Gp
| 0S***76 | Bolt 5.08 cm(2 In.) Long | 12 |
| 4D***04 | Washer,Flat Cover Mtg,Accessory Drive | 12 |
| 4N***14 | Gear; (113-Teeth)(Flywheel Starter) | 1 |
126-7281 Gear Gp-Front
| 0S***71 | Screw,Cap,Hexagon; Tube Assembly To Turbocharger And Elbow Mounting | 1 |
| 10***13 | Plate-Retaining | 1 |
| 11***17 | Plate-Thrust | 1 |
4n-3825 Gear Gp-Rear
| 1B***75 | Bolt (" " " ); Bolt ( " " " ) | 4 |
| 4N***25 | Gear Group-Rear; Rear Timing Gear Group | 1 |
| 4W***85 | Gear-Camshaft; (86-Teeth) | 1 |
4n-9680 Governor Gp-Air Compressor
| 2S***23 | Cover As; (Governor) | 1 |
| 4N***80 | Governor Group-Air Compressor | 1 |
| 9M***02 | Kit; (Governor Overhaul) (Includes Cover, Gasket, Grommet, Spring, Filter, Valve And Ring) | 1 |
7c-3617 Housing Gp-Flywheel
| 0S***91 | Screw,Cap,Hexagon Bearing Retainer; Part Of Kit P/N 1w***82 | 1 |
| 16***94 | Gasket | 1 |
| 1C***51 | Bolt--Installation Of 2v***26 Retainer | 2 |
126-7280 Housing Gp-Front
| 0L***52 | Capscrew (3/8 - 16 Nc X 3 1/4 Gd8, Hex) | 2 |
| 0T***73 | Bolt (3/8) (63.5mm Long) (On Cab Of Cover Assem.) | 3 |
| 12***80 | Housing Group-Front | 1 |
126-2267 Lifting Gp-Engine
| 0S***87 | Bolt-Bracket Assembly To Timing Gear | 4 |
| 11***75 | Bracket-Lifting; (Right) | 1 |
| 11***15 | Bracket-Lifting; (Left) | 1 |
114-5213 Lines Gp-Air Compressor
| 03***49 | Elbow; (90 Degree, 37 Degree Flared) | 1 |
| 03***69 | Elbow-Flared; (1/2-14 Nptf) | 1 |
| 0S***09 | Bolt (3/4") Filler Tube Assembly To Transfer Drive Case | 1 |
4n-8335 Lines Gp-Air Compressor
| 03***49 | Elbow; (90 Degree, 37 Degree Flared) | 1 |
| 0L***52 | Capscrew (3/8 - 16 Nc X 3 1/4 Gd8, Hex) | 1 |
| 0S***17 | Bolt --Use Open Hole In Compressor Body | 2 |
6i-3744 Pan Gp-Oil -Engine
| 11***14 | Pan-Oil; (Engine Oil) | 1 |
| 2P***03 | Bolt-Washer Head; (3/8-16x1.25-In) | 32 |
| 4N***51 | Gasket; (Engine Oil Pan) | 1 |
192-8808 Piston & Rod Gp
| 13***61 | Ring-Piston; (Top)(Top) | 1 |
| 15***56 | Bolt-Special; (Oil Jet) | 1 |
| 16***78 | Rod As-Connecting | 1 |
125-9323 Plug Gp-Cylinder Block
| 12***23 | Plug Group-Cylinder Block | 1 |
| 6V***89 | Seal-O-Ring (Id=19.18mm) | 3 |
| 7W***34 | Plug-Pipe (3/8-18 Nptf Thd) | 6 |
126-1336 Plug Gp-Cylinder Head
| 12***36 | Plug Group-Cylinder Head | 1 |
| 4N***32 | Plug-Cup | 2 |
| 5P***63 | Plug-Cup | 3 |
107-1954 Rocker Arm Gp
| 10***54 | Rocker Arm Group | 1 |
| 10***03 | Screw; (3/8-24x1.67-In)(Intake) | 2 |
| 12***63 | Bracket-Shaft | 1 |
319-0785 Seal Gp-Crankshaft -Rear
| 14***68 | Seal-Crankshaft; (Rear)(Flywheel Housing) | 1 |
| 31***85 | Seal Group-Crankshaft; -Rear | 1 |
319-7401 Seal Gp-Crankshaft -Front
| 14***67 | Seal Group-Crankshaft; (Front) | 1 |
| 31***01 | Seal Group-Crankshaft; -Front | 1 |
7e-6385 Support Gp-Engine
| 0S***66 | Bolt-Pulley To Crankshaft Adapter | 4 |
| 4D***04 | Washer,Flat Cover Mtg,Accessory Drive | 4 |
| 4N***84 | Support-Front Engine | 1 |
4n-4303 Trunnion Gp-Engine
| 0S***73 | Bolt (102mm Long); (1/2-13x4-In) | 6 |
| 4N***03 | Trunnion Group-Engine; Engine Trunnion Group | 1 |
| 4W***50 | Adapter-Support | 1 |
108-1551 Valve Mechanism Gp
| 0L***43 | Bolt 63.5 mm (3/8" X 2 1/2" -Cover Assembly To Fender | 8 |
| 10***89 | Bridge-Valve | 16 |
| 10***88 | Valve Lifter Assem | 16 |
Cooling System
134-5954 Lines Gp-Water
| 0L***43 | Bolt 63.5 mm (3/8" X 2 1/2" -Cover Assembly To Fender | 1 |
| 0S***87 | Bolt-Bracket Assembly To Timing Gear | 5 |
| 0S***88 | Bolt,Machine; Hose Assembly Mounting,Hose Assembly To Transmission,And To Torque Converter | 6 |
308-2242 Lines Gp-Water
| 0S***71 | Screw,Cap,Hexagon; Tube Assembly To Turbocharger And Elbow Mounting | 3 |
| 0S***90 | Bolt; (3/8-16x2in)(Clip Thru Spacer To Bracket As) | 3 |
| 0S***19 | Bolt,Machine Gear Retaining Part Of Kit P/N 1w***46 | 1 |
110-3017 Lines Gp-Water
| 0S***71 | Screw,Cap,Hexagon; Tube Assembly To Turbocharger And Elbow Mounting | 3 |
| 0S***90 | Bolt; (3/8-16x2in)(Clip Thru Spacer To Bracket As) | 3 |
| 0S***19 | Bolt,Machine Gear Retaining Part Of Kit P/N 1w***46 | 1 |
4n-1951 Pump Gp-Water
| 10***49 | Adapter-Inlet | 1 |
| 11***79 | Seal-O-Ring | 1 |
| 11***80 | Seal-O-Ring | 1 |
137-1338 Pump Gp-Water
| 0S***91 | Screw,Cap,Hexagon Bearing Retainer; Part Of Kit P/N 1w***82 | 1 |
| 10***30 | Bearing As-Roller | 1 |
| 11***21 | Plug-Felt; (Water Pump Housing) | 1 |
Electrical And Starting System
109-0400 Control & Mtg Gp-Engine Elek
| 10***00 | Control & Mtg Group-Engine Elek | 1 |
| 12***74 | Screw-Pan Head; (8-32x9.52-mm) | 1 |
| 13***26 | Washer; (4.52x8.28x0.76-mm Thk) | 1 |
156-7172 Control Gp-Engine Electronic
| 12***44 | Control Group-Governor | 1 |
| 15***72 | Control Group-Engine Electronic | 1 |
| 8C***54 | Cap-Receptacle | 1 |
322-7931 Conversion Gp-Alternator & Dec
| 10***03 | Kit; (Receptacle) (3-Pin) (Includes Receptacle As & Wedge) | 1 |
| 18***35 | Pin-Connector; (16-Ga To 18-Ga) | 3 |
| 32***31 | Conversion Group-Alternator & Dec | 1 |
204-7949 Sensor Gp-Position
| 15***60 | Kit-Connecting Plug; (3-Pin)(Engine Sensor Wiring Harness) | 1 |
| 18***36 | Socket-Connector; (16-Ga To 18-Ga) | 3 |
| 20***49 | Sensor Group-Position; -Throttle | 1 |
161-9931 Sensor Gp-Pressure
| 15***60 | Kit-Connecting Plug; (3-Pin)(Engine Sensor Wiring Harness) | 1 |
| 16***31 | Sensor Group-Pressure; -Atmospheric | 1 |
| 9X***13 | Sleeve (Order By cm)(Use As Required) | 0 |
167-1709 Sensor Gp-Pressure
| 15***60 | Kit-Connecting Plug; (3-Pin)(Engine Sensor Wiring Harness) | 1 |
| 16***09 | Sensor Group-Pressure; -Injection Actuation Oil | 1 |
| 18***40 | Socket-Connector; (14-Ga To 18-Ga)(14-Ga To 18-Ga) | 3 |
194-6725 Sensor Gp-Pressure
| 10***13 | Seal; (3 Pin Plug) | 1 |
| 15***60 | Kit-Connecting Plug; (3-Pin)(Engine Sensor Wiring Harness) | 1 |
| 18***36 | Socket-Connector; (16-Ga To 18-Ga) | 3 |
194-6722 Sensor Gp-Pressure
| 15***60 | Kit-Connecting Plug; (3-Pin)(Engine Sensor Wiring Harness) | 1 |
| 19***26 | Harness As-Sensor; (16-18 Ga Wire)(Engine Oil Temperature) | 3 |
| 19***22 | Sensor Group-Pressure; -Atmospheric Air | 1 |
194-6724 Sensor Gp-Pressure
| 15***60 | Kit-Connecting Plug; (3-Pin)(Engine Sensor Wiring Harness) | 1 |
| 18***40 | Socket-Connector; (14-Ga To 18-Ga)(14-Ga To 18-Ga) | 3 |
| 19***24 | Sensor Group-Pressure; -Air Inlet Manifold | 1 |
265-9033 Sensor Gp-Speed
| 10***03 | Kit; (Receptacle) (3-Pin) (Includes Receptacle As & Wedge) | 1 |
| 18***35 | Pin-Connector; (16-Ga To 18-Ga) | 3 |
| 26***33 | Sensor Group-Speed; -Engine | 1 |
129-6628 Sensor Gp-Speed
| 12***28 | Sensor Group-Speed; -Engine Speed/Timing | 1 |
| 15***60 | Kit-Connecting Plug; (3-Pin)(Engine Sensor Wiring Harness) | 2 |
| 19***26 | Harness As-Sensor; (16-18 Ga Wire)(Engine Oil Temperature) | 3 |
102-2240 Sensor Gp-Temperature
| 10***40 | Sensor Group-Temperature; -Output Transfer Gear Oil | 1 |
| 10***03 | Kit; (Receptacle) (3-Pin) (Includes Receptacle As & Wedge) | 1 |
| 18***35 | Pin-Connector; (16-Ga To 18-Ga) | 3 |
106-0735 Sensor Gp-Temperature
| 10***35 | Sensor Group-Temperature; -Engine Oil | 1 |
| 17***08 | Switch Group-Flow; -Engine Coolant | 1 |
| 2B***95 | Cap Screw--Tube Assembly To Air Inlet Pipe | 2 |
100-4417 Switch Gp-Flow
| 0S***09 | Bolt (3/4") Filler Tube Assembly To Transfer Drive Case | 1 |
| 0S***94 | Bolt (1 In. Long 3/8 In. Dia.); Plate Assembly To Support Assembly | 1 |
| 0S***20 | Bolt--Customer Grounding Bolt | 1 |
121-4082 Wiring Gp-Engine Electronic
| 03***34 | Seal-O-Ring | 1 |
| 10***61 | Clip | 1 |
| 11***30 | Receptacle As-Connector; (4-Pin) | 1 |
109-0401 Wiring Gp-Unit Injector
| 10***01 | Wiring Group-Unit Injector | 1 |
| 3H***75 | Pin-Spring; (Spring) | 1 |
| 6N***61 | Core As-Oil Cooler; (Transmission) | 1 |
Engine Arrangement
225-0402 Conversion Ar-Engine
| 22***96 | Engine Ar | 1 |
| 22***02 | Conversion Ar-Engine | 1 |
| 32***31 | Conversion Group-Alternator & Dec | 1 |
225-0396 Engine Ar
| 10***17 | Switch Group-Flow; -Engine Coolant | 1 |
| 10***19 | Cylinder Head Group | 1 |
| 10***47 | Camshaft Group | 1 |
Fuel System
126-9544 Control Gp-Governor
| 11***35 | Pin | 1 |
| 12***44 | Control Group-Governor | 1 |
| 18***49 | Drive Group-Unit Inj Hydraulic Pump | 1 |
180-6649 Drive Gp-Unit Inj Hyd Pump
| 11***98 | Adapter-Injection | 1 |
| 11***22 | Seal-Rectangular | 1 |
| 13***69 | Bolt-Socket Head | 2 |
125-3428 Drive Gp-Unit Inj Hyd Pump
| 03***01 | Bolt; --To Reverse Shaft Bearing Retainer | 2 |
| 0S***18 | Bolt; (5/16-18x1-In)(Hydraulic Pump) | 2 |
| 12***40 | Plate | 1 |
232-1168 Injector Gp-Fuel
| 23***68 | Injector Group-Fuel | 1 |
198-7912 Injector Gp-Fuel
| 11***98 | Adapter-Injection | 1 |
| 11***22 | Seal-Rectangular | 1 |
| 13***69 | Bolt-Socket Head | 2 |
166-5985 Kit-Compensator
| 03***53 | Seal-O-Ring; (08.92mm Id) | 3 |
| 03***27 | Seal-O-Ring; (19.18mm Id) | 2 |
| 03***39 | Seal-O-Ring (Id=9.25mm) | 1 |
138-6256 Kit-Seal -Unit Injector Hydraulic Pump
| 03***33 | Seal-O-Ring; (12.42mm Id) | 4 |
| 09***87 | Tee | 1 |
| 0L***51 | Bolt Starting Engine Fuel Tank Bracket To Diesel Intake Manifold | 2 |
126-7291 Lines Gp-Fuel Filter
| 0L***43 | Bolt 63.5 mm (3/8" X 2 1/2" -Cover Assembly To Fender | 2 |
| 0S***88 | Bolt,Machine; Hose Assembly Mounting,Hose Assembly To Transmission,And To Torque Converter | 1 |
| 10***02 | Tube As | 1 |
121-4034 Lines Gp-Injector Hyd Pump
| 03***33 | Seal-O-Ring; (12.42mm Id) | 1 |
| 0L***70 | Bolt (2-1/4") Filler Tube Assembly To Transfer Drive Case | 1 |
| 0S***17 | Bolt --Use Open Hole In Compressor Body | 4 |
126-7292 Pump & Mtg Gp-Unit Inj Hyd
| 03***33 | Seal-O-Ring; (12.42mm Id) | 1 |
| 0L***70 | Bolt (2-1/4") Filler Tube Assembly To Transfer Drive Case | 1 |
| 0S***17 | Bolt --Use Open Hole In Compressor Body | 4 |
206-2630 Pump Gp-Fuel Injection
| 10***77 | Valve Group-Solenoid; -Pressure Control | 1 |
| 13***52 | Seal-O-Ring | 1 |
| 13***09 | Fitting | 2 |
225-0568 Pump Gp-Unit Injector Hyd
| 0S***17 | Bolt --Use Open Hole In Compressor Body | 4 |
| 11***20 | Coupling | 1 |
| 14***50 | Pump Group-Fuel Transfer | 1 |
235-2024 Pump Gp-Unit Injector Hyd
| 03***39 | Seal-O-Ring (Id=9.25mm) | 2 |
| 03***42 | Seal-O-Ring; (11.89mm Id) | 3 |
| 13***05 | Gasket-Housing | 1 |
235-2026 Pump Gp-Unit Injector Hyd
| 03***33 | Seal-O-Ring; (12.42mm Id) | 1 |
| 23***26 | Pump Group-Unit Injector Hydraulic | 1 |
| 6V***89 | Seal-O-Ring (Id=19.18mm) | 1 |
225-0567 Pump Gp-Unit Injector Hyd
| 0S***17 | Bolt --Use Open Hole In Compressor Body | 4 |
| 11***20 | Coupling | 1 |
| 14***50 | Pump Group-Fuel Transfer | 1 |
102-7535 Valve Gp-Check
| 03***43 | Seal-O-Ring | 1 |
| 10***35 | Valve Group-Check; -Fuel Return Port | 1 |
| 10***06 | Seal-O-Ring (10.52mm Id) | 1 |
190-0016 Valve Gp-Fuel
| 03***27 | Seal-O-Ring; (19.18mm Id) | 2 |
| 03***28 | Seal-O-Ring | 1 |
| 10***03 | Seal-O-Ring; (7.65mm Id) | 1 |
161-2309 Valve Gp-Fuel
| 03***53 | Seal-O-Ring; (08.92mm Id) | 3 |
| 10***77 | Valve Group-Solenoid; -Pressure Control | 1 |
| 16***09 | Valve Group-Fuel | 1 |
165-1536 Valve Gp-Pressure Control
| 03***28 | Seal-O-Ring | 1 |
| 03***39 | Seal-O-Ring (Id=9.25mm) | 1 |
| 12***32 | Ring-Backup | 1 |
107-0677 Valve Gp-Solenoid
| 10***77 | Valve Group-Solenoid; -Pressure Control | 1 |
| 11***69 | Spacer-Special; (8.2x25x89.7-mm Thk) | 4 |
| 15***72 | Control Group-Engine Electronic | 1 |
Lubrication System
119-8583 Fastener Gp-Oil Pump Mounting -Engine
| 0L***43 | Bolt 63.5 mm (3/8" X 2 1/2" -Cover Assembly To Fender | 1 |
| 0S***19 | Bolt,Machine Gear Retaining Part Of Kit P/N 1w***46 | 2 |
| 11***83 | Fastener Group-Oil Pump Mounting; -Engine | 1 |
127-9374 Filler Gp-Engine Oil
| 12***74 | Filler Group-Engine Oil | 1 |
| 12***97 | Tube As | 1 |
| 12***98 | Tube As-Oil Filler | 1 |
125-8280 Filler Gp-Engine Oil
| 0S***88 | Bolt,Machine; Hose Assembly Mounting,Hose Assembly To Transmission,And To Torque Converter | 1 |
| 12***81 | Tube As | 1 |
| 12***80 | Filler Group-Engine Oil | 1 |
4n-2357 Filter Gp-Engine Oil
| 0S***71 | Screw,Cap,Hexagon; Tube Assembly To Turbocharger And Elbow Mounting | 4 |
| 1R***16 | Filter As-Engine Oil; (Standard Efficiency) | 2 |
| 2P***03 | Base As-Oil Filter; (Engine) | 2 |
128-0947 Gauge Gp-Oil Level (Dipstick) -Engine
| 0L***43 | Bolt 63.5 mm (3/8" X 2 1/2" -Cover Assembly To Fender | 1 |
| 11***68 | Seal-O-Ring; (15.54mm Id) | 1 |
| 12***54 | Tube As | 1 |
125-8279 Gauge Gp-Oil Level (Dipstick) -Engine
| 06***39 | Seal-O-Ring | 1 |
| 0L***51 | Bolt Starting Engine Fuel Tank Bracket To Diesel Intake Manifold | 1 |
| 0S***94 | Bolt (1 In. Long 3/8 In. Dia.); Plate Assembly To Support Assembly | 1 |
125-8277 Lines Gp-Engine Oil
| 0L***51 | Bolt Starting Engine Fuel Tank Bracket To Diesel Intake Manifold | 1 |
| 0S***71 | Screw,Cap,Hexagon; Tube Assembly To Turbocharger And Elbow Mounting | 1 |
| 0S***88 | Bolt,Machine; Hose Assembly Mounting,Hose Assembly To Transmission,And To Torque Converter | 2 |
125-8278 Lines Gp-Filter
| 06***40 | Seal-O-Ring (Id=37.69mm) | 4 |
| 0L***70 | Bolt (2-1/4") Filler Tube Assembly To Transfer Drive Case | 1 |
| 0S***71 | Screw,Cap,Hexagon; Tube Assembly To Turbocharger And Elbow Mounting | 4 |
129-5250 Lines Gp-Turbocharger Oil
| 0L***43 | Bolt 63.5 mm (3/8" X 2 1/2" -Cover Assembly To Fender | 1 |
| 0S***09 | Bolt (3/4") Filler Tube Assembly To Transfer Drive Case | 1 |
| 0S***71 | Screw,Cap,Hexagon; Tube Assembly To Turbocharger And Elbow Mounting | 2 |
116-1980 Pump Gp-Engine Oil
| 10***82 | Shaft As-Pump Drive | 1 |
| 10***73 | Shaft As-Idler | 1 |
| 11***79 | Body As-Oil Pump | 1 |
Power Train
4n-2210 Cooler Gp-Transmission Oil
| 3N***90 | Plate Serial Number; On R.H. Rear Bank Of Cylinder Block As Viewed From Rear Of Engine | 1 |
| 4N***10 | Cooler Group-Transmission Oil; Oil Cooler Group--Transmission | 1 |
Service Equipment And Supplies
126-2334 Plate & Film Gp
| 12***34 | Plate & Film Group | 1 |
637D serial number reference
The PIN plate is typically located on the machine outer frame. The prefix consists of the first three alphanumeric characters of the serial number, which identifies the model and manufacturing factory.
| Prefix | Identifies | Notes |
|---|---|---|
| 20W | 637D Scraper (Machine) | Configuration: 20W00001-00494; Powered by 3306 engine; confirm with dealer for other configurations/series. |
Frequently asked questions
What engine powers the Caterpillar 637D?
The Caterpillar 637D tractor unit is powered by a Caterpillar 3306 engine.
What is the overall dimension of the 637D?
The machine has an overall length of 48.56 ft (14.80 m), an overall width of 13 ft (3.96 m), and an overall height of 13.69 ft (4.17 m).
What models succeeded the 637D in the Caterpillar lineage?
The 637D was followed by subsequent generations including the 637E, 637G, and the current flagship 637K.
What 637D owners discuss
What causes diesel fuel to accumulate in the hydraulic tank during operation?
Fuel entering the hydraulic tank while the engine is running may be caused by crossed lines at the filter locations. On certain configurations, two fuel filters and two hydraulic filters are positioned on the front of the hydraulic tank; if these lines are misconnected, fuel can migrate into the hydraulic system. Additionally, check for potential leaks in ejector cylinder head or barrel seals that might allow fluid transfer via drain hoses.
What is the typical fuel return flow rate for the rear engine injection pump?
The fuel return flow rate from the rear engine fuel injection pump is approximately 9 gallons per hour.
Which hydraulic oil specification should be used for Caterpillar systems?
For hydraulic systems, use Cat HYDO Advanced oils. To prevent sludge and valve damage, avoid exceeding a 10% cross-contamination rate when switching between different oil types.
What are the primary engine oil requirements for Caterpillar diesel engines?
Standard diesel engine oil requirements include Cat DEO (Diesel Engine Oil) and Cat DEO-ULS (Ultra Low Sulfur). For North American, Mexican, and US applications, SAE 15W-40 or SAE 10W-30 are common weights. Cold weather applications may require SAE 0W-40.
What should be inspected on the frame of a used scraper before purchase?
Inspect the frame rails and flanges for cracks, particularly in units that have been used in heavy-duty environments like logging. Check the area where the saddle bolts to the block for the equalizer spring, as bolt holes can break out under stress.
What is a critical warning sign of engine failure regarding oil condition?
Milky appearance in the oil indicates coolant contamination, which is often a sign of head gasket failure. Have your dealer verify the engine's internal condition via S·O·S services.
Compiled from owner and technician discussions across the industry — experiences vary by serial range and machine history.
Serial-range & configuration variants
This page covers the Caterpillar 637D. Related factory variants of the same model family:
637D
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