631G Wheel Tractor Scraper

631G Wheel Tractor Scraper

Caterpillar Wheel Tractor-Scrapers offer fast cycle times, with quick loading, high travel speeds and the ability to load and dump on the run. Rugged construction and easy maintenance assure long life with low operating costs.

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Power Train - Engine

A combination of innovations working at the point of combustion, ACERT™ technology optimizes engine performance while meeting regulations for off-road applications.

Cat C18 Tractor Engine

The tractor for the 631G is powered by the C18 engine with ACERT™ Technology. The large displacement and high torque rise provide optimal performance in the load, cut, haul and return. Matched to the high efficiency torque converter and electronically controlled power shift transmission, it will provide years of dependable service.

Cat C9 Scraper Engine

The 637G has a C9 engine with ACERT technology which provides additional power to assist in loading as well as improved hauling performance on grades.

Dual Horsepower

Cat engines have dual horsepower capability with the low power setting in torque converter drive and the high power setting in direct drive.

Mechanical Electronic Unit Injection (MEUI)

The MEUI system with variable shaped injection patterns provides for optimum combustion based on altitude and temperature. The Cat MEUI fuel system is a highly evolved fuel system with a proven record of reliability in the field. The system combines the technical advancement of an electronic control system with the simplicity of direct mechanically controlled unit fuel injection pressure. These features allow the C18 to completely control injection timing, duration and pressure.

Electronic Control Module

The ECM responds to operator commands and engine sensor input to optimize engine and machine performance. This advanced engine management software controls and protects the engine at all times against cold starts, high altitude operations and air filter plugging by monitoring:

  • injection timing and pressure
  • engine cooling fan speed
  • ether starting aid
  • hydraulic pumps

NGMR Engine Cooling System

The standard radiator for the tractor is the Next Generation Modular Radiator (NGMR), which features 9 fins per inch rather than 33 fins per inch found on previous models. The increased radiator fin spacing for both the tractor and the scraper reduces clogging in severe applications. Two-piece service doors improve access to clean out debris.

Extended Oil Change Interval

Oil change intervals in the C18 engine can be extended to 500 hours with the use of S•O•SSM analysis.

Power Train - Transmission

Integrated electronics allow the machine to monitor the entire power train, reducing component stress and providing a better ride.


Electronically controlled Caterpillar planetary powershift transmission with eight forward and one reverse speed. Tractor gears 1 & 2 operate in converter drive for increased torque capability during cut and fill operations. Gears 3-8 operate in direct-drive for drive train efficiency during the haul. All scraper gears operate in converter drive for increased torque capability during the cut and fill.

Final Drives

Outboard-mounted, planetary design final drives reduce torque loads on other power train components. Large-capacity, double-row roller bearings and Caterpillar Duo-Cone® seals deliver exceptional reliability in the toughest applications.

Independent Brake Systems

Expanding-shoe type brakes use a cam-operated design, which is air-applied and spring released. The secondary braking system uses independent front and rear circuits that are automatically applied if the service air pressure drops to 55 psi (380 kPa). Audible and visual action alert indicators inform the operator when the service air pressure drops to 75 psi (518 kPa).


Full hydraulic power steering provides automotive feel with positive, modulated flow control for constant steering response. An optional supplemental steering system is ground-driven and provides hydraulic power for steering if needed.


Superior structural design and construction optimize performance and reliability.

Cushion Hitch

The electronically actuated cushion hitch incorporates a parallelogram-type linkage for exceptional strength. Twin nitrogen accumulators help deliver a smooth ride for enhanced operator comfort.

  • cushion hitch lock down control for positive cutting edge down pressure when loading or spreading
  • controlled oil flow dampens rebound oscillation
  • leveling valve automatically centers piston in cylinder for all loads
  • steel castings are used extensively to eliminate many welded joints and increase strength
  • double-kingbolt design withstands high external forces and simplifies installation and removal

Nitrogen Accumulators

Vertically mounted hydraulic cylinder transfers road shocks to nitrogen accumulators. They absorb and dampen road shocks, thus reducing loads from being transmitted to the operator.

Lockout Switch

An operator-selectable lockout switch, located on the joystick, locks the cushion hitch for improved control of the cutting edge during loading and dumping.

Operator Station

State-of-the-art productivity and operator comfort.

Multi-Adjustable Seat

The Cat Comfort Cloth Seat offers an adjustable seat and armrests for maximum operator comfort.

  • Swivels and locks in four positions (0º - 10° - 20° - 30º) providing the optimum operating position in the cut or on the haul.
  • Adjustable 4 in. (102 mm) fore/aft and 8 in. (203 mm) vertical height to accommodate various sized operators.
  • Static seat belt is standard. A retractable non-cinching seat belt is available as an option.

Revised Steering Column

Increases legroom a full 3.5 in. (89 mm), and reduces knee contact.

Standard Air Conditioning

Standard air conditioning system with relocated louvers enhances airflow in the cab.

Storage And Amenities

Convenient storage location includes space for a lunch box and first aid kit. The cab also has a cup holder as well as an ashtray.


The redesigned hood has sloped corners to maximize visibility while accommodating the low emissions engine. The redesigned hood and front shroud are wider to enclose the air-to-air aftercooler (ATAAC), ether starting aid, and lights. The exhaust is located at the back of the hood for good visibility to the right side.

Instrument Display Panel

Features a new quad-gauge layout showing engine coolant temp, transmission / torque converter oil temp, fuel level, and system air pressure.

Engine Speed Lock Controller

Enhances operation during long haul cycles by allowing the operator to maintain a desired engine speed without maintaining pressure on the throttle.

Simplified Transmission Control

Simplifies gear selection (1st, 2nd, Drive and Reverse) and allows operator-defined top gear control. Relocating the gear control to the rear increases operator legroom.

Grab Handle / Hand Rest

The grab handle/hand rest located next to the joystick controller helps operators when adjusting seat swivel, and gives them a place to rest their hand while on the haul and return roads.

Single Lever Implement Control

Simple and easy to operate, the joystick enhances the productivity of operators of all skill levels. Requires less force to control the critical scraper functions and requires less lever travel. 1) Bowl (forward & back) 2) Ejector (side to side) 3) Apron (thumb rocker switch) 4) Transmission Hold 5) Cushion Hitch 6) Rocker switch (not shown - is on front of joystick) • Push-Pull (bail up/down) * Standard open bowl does not have a rocker switch.

Electronic Controls

Integrated electronic controls provide smooth, consistent shifts through the synchronization of engine and transmission speeds.

Simplified System

The electrical system has been redesigned to utilize three electronic control modules (ECM) on the tractor instead of four.

Improved Serviceability

Combined monitoring systems, easy access diagnostics and more durable components make routine maintenance and servicing simple and fast.

Product Link

Product Link is a wireless system that allows the customer to track machine data such as location, service meter hours as well as machine health information. The system can automatically issue alerts when the machine is operated beyond owner-defined time and location limits. Product Link is available as a factory attachment or it may be installed in the field, in that there is a mounting location for the module as well as an antenna on the machine. A wiring breakout is standard, without having to splice into existing wires.

Fuel Economy

Electronic controls optimize the timing setting for varying conditions. The ADEM A4 controller matches timing to the load on the engine, engine rpm and temperature.

Reduced Exhaust Smoke

The ADEM A4 controller monitors electronic sensors to determine the optimum fuel/air ratio. Fuel is precisely controlled during cranking, starting and acceleration to reduce smoke. The Engine Electronics are faster and more efficient than mechanically controlling the governor rack position.

Scraper Bowl

Designed for optimum loading, material retention and ejection.

Redesigned Bowl

The redesigned bowl minimizes falling material lodging between the bowl and the draft arm, which can result in premature wear. The modifications also provide better load retention on level ground or traversing down a grade. Bowl capacity has been increased by 3 yd3 (2.3 m3), allowing more material to be moved.

  • Low-profile bowl design offers less resistance to incoming materials.
  • Cellular construction adds strength and dent resistance to bowl sides and floor.

Bulldozer Ejection System

Cat bulldozer ejection system offers constant spreading control with minimal material carry back. A spill guard helps retain material and keep it from spilling over onto the rear of the scraper (optional on single engine open bowl scrapers).

Cutting Edges

May be adjusted according to job conditions. The stinger (drop down) position provides good penetration and efficient flow of material into the bowl, whereas the level cutting edge is used for finish work or very high impact conditions.

Material Application

Well suited to handle a wide variety of material from clay to shot rock.


To achieve maximum productivity, the 631G should be push loaded by a D9R or D10R Track-Type Tractor. The larger tractor offers quicker loading times with denser loads than the smaller tractor.


Count on Caterpillar for simplified service and the most productive uptime.

Grouped Service Points

Maintenance and service points for the engine are grouped on the right-hand side for easy access. They include the engine air cleaner, engine oil check and fill, fuel filters and priming, coolant level sight glass, window washer bottle, air conditioning dryer cartridge, ether starting aid canister, engine oil filter, fan drive lubrication, and sampling ports for the engine oil and coolant.

  • Spin-on fluid filters for all but the main hydraulic filter
  • Cab wiring harness redesigned and relocated for better serviceability

Customer Support

Cat dealer services help you operate longer with lower costs.

Product Support

You will find nearly all parts at our dealer parts counter. Cat dealers use a world-wide computer network to find in-stock parts to minimize machine down time. To save money use genuine Cat Reman parts whenever possible. You receive the same warranty and reliability as new products at substantial cost savings.

Machine Selection

Make detailed comparisons of the machines under consideration before purchase. Cat dealers can estimate component life, preventive maintenance cost, and the true cost of lost production.


Look past initial price. Consider the financing options available as well as day-to-day operating costs. Look at dealer services that can be included in the cost of the machine to yield lower equipment owning and operating costs over the long run.

Customer Support Agreements

Cat dealers offer a variety of product support agreements, and work with customers to develop a plan that best meets specific needs. These plans can cover the entire machine, including attachments, to help protect your investment.


Improving operating techniques can boost your profits. Your Cat dealer has videotapes, literature and other ideas to help you increase productivity, and Caterpillar offers certified operator training classes to help maximize the return on your machine investment.

Maintenance Services

Talk to your dealer about the range of available maintenance services. Repair option programs guarantee the cost of repairs up front. Diagnostic programs such as S•O•SSM Analysis and Coolant Sampling and Technical Analysis help avoid unscheduled repairs.


Repair, rebuild or replace? Your Cat dealer can help you evaluate the cost involved so you can make the right choice.

Tractor Engine

Flywheel Power: Tractor/Scraper
373 kW (500 hp)
Net Power
345/373 kW 462/500 hp
Gross Power - Gears 1-2
Gross Power - Gears 3-8
Net Power - Gears 1-2
Net Power - Gears 3-8

Scraper Bowl

Scraper Capacity: Heaped
Rated Load
Capacity Struck
Depth of Cut - max.
Width of Cut, to Router Bits
Ground Clearance - max.
Cutting Edge - thickness
Hyd. Penetration Force - 631G
Depth of Spread - max.
Apron Opening
Apron Closure Force


Top Speed (Loaded)
1 Forward
2 Forward
3 Forward
4 Forward
5 Forward
6 Forward
7 Forward
8 Forward


Tractor Engine
Cat® C18 ACERT™


Operating Weight

Weights - Standard, tandem

Total Shipping
Total Operating - empty
Front Axle
Rear Axle
Total Operating - loaded
Front Axle Weight - loaded
Rear Axle Weight - loaded


Width - Overall Machine
Width - Tractor
Width - rear tire center lines
Width - Inside of Bowl
Width - Outside Rear Tires
Height - Overall Shipping
Height - Top of Cab
Ground Clearance - Tractor
Front of Tractor to Front Axle
Axle to Vertical Hitch Pin
Height - Scraper Blade Maximum
Length - overall machine
Rear Axle to Rear of Machine


Width - 180° Turn
Steering Angle - Right
Steering Angle - Left

Service Refill Capacities - Tractor

Fuel Tank - 631G
Final Drive (per side)
Cooling System
Hydraulic Reservoir
Wheel Coolant (each)
Windshield Washer


Bowl Cylinder Bore
Bowl Cylinder Stroke
Apron Cylinder Bore
Apron Cylinder Stroke
Ejector Cylinder Bore
Ejector Cylinder Stroke
Steering Circuit
Scraper Circuit
Cushion Hitch Circuit
Secondary Steering Circuit
Relief Valve - Steering Circuit
Relief Valve - Implement Circuit
Compensator Setting - Cushion Hitch Circuit

Service Refill Capacities - Scraper

Wheel Coolant (each)

Transmission - 631G

1 Forward
2 Forward
3 Forward
4 Forward
5 Forward
6 Forward
7 Forward
8 Forward

Standard Equipment

  • Electrical
    • Alarm, backup
    • Alternator, 75 amp
    • Batteries (4), 12V Maintenance Free, High Output
    • Electrical System, 24V
    • Lighting System
      • Directional Signals; Hazard Lights; Headlights, halogen with dimmer; Floodlight, Cutting edge
    • Starting Receptacle
  • Operator Environment
    • Air Conditioner (includes heater and defroster)
    • Cigarette Lighter and Ashtray
    • Coat Hook
    • Diagnostic Connection Port (12V)
    • Dome Courtesy Light
    • Gauge Group
      • Air Pressure
      • Converter/Retarder temperature
      • Electronic Monitoring System (EMS III)
      • Engine coolant temperature
      • Actual Transmission Gear Indicator
      • Fuel
      • Speedometer
      • Tachometer
      • Transmission gear indicator
    • Horn
    • Implement Control Joystick
    • Rearview Mirrors
    • Radio Ready (two radio openings, speakers, and 5-amp converter)
    • ROPS Cab with Sound Suppression and Pressurization
    • Static Seatbelt
    • Seat, Air Suspension, Caterpillar Comfort, cloth
    • Steering Wheel - tilt and telescoping
    • Storage Compartment
    • Throttle Lock
    • Transmission Hold
    • Windows - sliding side, swing out
    • Windshield - laminated glass
    • Windshield Wiper/Washer - front and rear
  • Power Train
    • Engine
      • Electric start, 24V
      • Fan, suction (steel spider with nylon blades)
      • Ground level engine shutdown
      • Muffler
      • Starting Aid, ether
      • Thermo-shield, exhaust manifold & turbo soft wrapped
    • Braking System
      • Parking/Primary/Secondary
      • Shields - brake
    • Transmission
  • Other Standard Equipment
    • Extended Life Coolant, -36° C (-33° F)
    • Fan hub, permanent lube
    • Fast Oil Change
    • Fenders
    • Rims - 35 inch (2)
    • Tires, 37.50-R35 radial
    • Tractor:
      • Air dryer
      • Cushion hitch
      • Locks, vandalism (oil fill, dipstick)
      • Product Link ready
      • Tow Pins - front and rear

Optional Equipment

  • Crankcase Guard, Heavy Duty
  • Extended Life Coolant, -50° C (-58° F)
  • Fan, Defrost
  • Fenders (scraper)
  • Fuel system - (fast-fill European Union Compliant)
  • Heater - jacket water
  • Hydraulic Retarder
  • Lights, Side Vision
  • Lock, Steering
  • Overflow Scraper Guard
  • Powertrain Guard
  • Retractable seat belts
  • Secondary Steering