844

Engineered for demanding work in large dozing applications, the Caterpillar 844 Wheel Dozer is an ideal match for power generating utilities, clean up, road maintenance and production dozing at mines and in the general contracting industry.


SPECIFICATIONS
Engine
Engine Model Cat® 3412E
Gross Power 675 hp
Flywheel Power 620 hp
Flywheel Power - Caterpillar 625 hp
Net Power 620 hp
Flywheel Power - EEC 80/1269 625 hp
Flywheel Power - ISO 9249 625 hp
Flywheel Power - SAE J1349 (JAN90) 618 hp
Flywheel Power - DIN 70020 648 PS
Bore 5.4 in
Stroke 6 in
Displacement 1649 in3


Weights
Operating Weight 156120 lb


Operating Specifications
Blade Capacities 15.9 to 30.7 m3 20.7 to 40.2 yd3
Ground Clearance 1.56 ft


Transmission
Converter Drive - Forward 1 4.4 mph
Converter Drive - Forward 2 7.6 mph
Converter Drive - Forward 3 13 mph
Converter Drive - Reverse 1 4.8 mph
Converter Drive - Reverse 2 8.4 mph
Converter Drive - Reverse 3 14.3 mph
Direct Drive - Forward 1 4.5 mph
Direct Drive - Forward 2 7.9 mph
Direct Drive - Forward 3 14 mph
Direct Drive - Reverse 1 4.9 mph
Direct Drive - Reverse 2 8.8 mph
Direct Drive - Reverse 3 15.4 mph
Number of Forward Speeds 3
Number of Reverse Speeds 3


Hydraulic System
Output at 2,126 rpm and 6894 kPa (1,000 psi) 89 gal/min
Cylinder, Double-Acting: Tilt and Tip, Bore and Stroke 209.5 mm x 188 mm 8.25 in x 7.5 in
Relief Valve Setting - Bulldozer (Large Pump) 2700 psi
Relief Valve Setting - Tilt Cylinders (Small Pump) 2920 psi


Steering
Minimum Turning Radius (Over Tires) 390 in
Hydraulic output at 2128 rpm and 1000 psi (6900 kPa) 108 gal/min
Relief Valve Setting 4500 psi
Steering Angle 35 Degrees


Service Refill Capacities
Fuel Tank - Standard 260 gal
Cooling System 50.2 gal
Crankcase 25 gal
Transmission 29 gal
Hydraulic Tank 141 gal
Differentials and Final Drives - Front 71.6 gal
Differentials and Final Drives - Rear 68.9 gal
Hydraulic System - Implement and Brakes (Tank Only) 45 gal
Hydraulic System - Steering and Engine Cooling Fan (Tank Only) 34.9 gal


Cab
ROPS/FOPS Meets SAE and ISO standards.
Sound Performance Levels Meets ANSI, SAE and ISO standards.


Axles
Front Fixed
Rear Oscillating ±11°
Maximum Single-Wheel Rise and Fall 22.5 in


Brakes
Brakes Meets SAE/ISO 3450 1996.


Tires
Tire Choices Two choices available.
Standard Tire Size Two choices available.


BENEFITS & FEATURES
Power Train
844 power train components deliver dependable, reliable performance customers expect from Cat wheel dozers.


Caterpillar 3412E Hydraulic Electronic Unit Injection Engine
Is rated at 466 kW net (625 hp) at 2,000 rpm. The HEUI fuel system and Electronic Control Module (ECM) deliver power and efficiency in the most demanding applications. Electronic control provides many benefits:
  • ADEM II (Advanced Diesel Engine Management II)
  • Automatic altitude deration
  • Elevated low idle
  • Cold weather starting mode
  • Acceleration delay on startup to reduce engine wear
  • Advanced diagnostic capabilities
  • Automatic control of ether aid
  • 500 hour oil change interval with CH-4 oil and new larger oil pan
  • Dry-type air cleaner with primary and secondary elements
  • Engine/torque divider module is isolation mounted to the main frame to reduce machine vibration and structure radiated noise
  • Monotherm pistons

Starting System
Is direct-electric 24-volt with a 75-amp alternator and two 12-volt 190-amp-hour batteries.

Injection Timing
Is controlled without concern for cam profile limitations. Complete control of engine speed provides advantages in lower emissions, quieter operation, reduced smoke, improved hot or cold starting, white smoke cleanup and high altitude operation.

Injection Duration
With the HEUI system will decrease proportionately with engine speed but can also electronically control the oil supply pressure. This complete control provides improved engine performance and decreased fuel consumption.

Injection Rate Shaping
Reduces nitrous oxide (NOx) emissions and reduces engine combustion noise.

1 Aftercooler
Lowers inlet charge temperature. Reduces thermal stresses that can cause premature wear of pistons, rings and liners.

2 High Injection Pressures
Independent of engine speed, decrease smoke and emissions while improving response.

3 Oil-Cooled Pistons and Full-Length, Water-Cooled Cylinder Liners
Provide maximum heat transfer for longer component life.

4 Engine Oil Cooler
Maintains optimum oil temperature for proper cooling and pressure lubrication. Engine cooling provided is by the Multi-Row Modular radiator. Hydrostatic fan drive gives the standard cooling package 110° F ambient capability.

Impeller Clutch Torque Converter (ICTC)
Allows the operator to modulate rimpull from 100 percent to 20 percent of maximum rimpull. After 20 percent of maximum rimpull is achieved, further pedal travel applies the brake. The torque converter is equipped with a lockup clutch for direct drive efficiency.

5 Impeller Clutch
Modulates the amount of engine power sent to the wheels.

6 Lockup Clutch
With Electronic Clutch Pressure Control provides direct drive efficiency in second and third forward gears and all three gears in reverse with higher speeds and improved fuel economy on long distance dozing.

ICTC Benefits
  • Improved calibration Procedure
  • Improved left pedal modulation
  • Compensates for wear and provides the ability to recalibrate for optimum left pedal modulation regardless of torque converter wear.

Planetary, Electronic, Power Shift Transmission
Is the same transmission found in the 990 Series II wheel loader. Electronic shifting provides smooth consistent shifts with finger tip controls housed in the STIC controller. The transmission is built around a center shaft with a gear set cluster stacked end-to-end to distribute load, conserve space and transfer energy efficiently. Large diameter perimeter clutches coupled with high contact planetary gear sets provide high torque carrying capacity for long, trouble-free life.

Parking Brake
Is spring-applied, oil-released and dry disc. It is mounted on the transmission gear output shaft. The Electronic Monitoring System III alerts the operator if the transmission is engaged while the parking brake is applied as well as if pressure drops, in which case the brake will automatically apply. Manual override is possible to allow movement of the machine.
  • Self-diagnostics accessible through Caterpillar Monitoring System
  • Quick Shift

7 Final Drives
Are planetary consisting of a ring gear, three planet gears, a planet gear carrier and a sun gear.
  • Ring gears splined to reation hub
  • Proprietary gear cutting and heat treat methods are used in the manufacturing of components
  • Full-floating bronze sleeve bearings are used on planet gears
  • Oil-bath lubrication

8 Axle-Shaft, Oil-Disc Brakes
Are fully hydraulic, completely sealed and never need adjustment. Disc face grooves provide cooling even when brakes are applied for a long, fade resistant life.

Design
Provides a larger cooling oil reservoir and thicker separator plates than conventional brake designs. This gives the brake higher heat dissipation rates allowing higher capacity than conventional oil-disc brakes. Duo-cone seals are located between the wheel and the spindle.

9 Brake Location
Reduces service time. Conventional brakes require final drive disassembly. The axle-shaft brake design allows brake service while leaving the final drive intact. Reduced service time and machine downtime keeps operating costs low.

Bevel Gear Sets and Differentials
Are common with the Cat 990 Series II Wheel Loader.

Service Brakes
Are four wheel, hydraulic, oil-dipped multiple disc brakes that are adjustment-free, completely enclosed and allow modulated engagement without slack adjusters.

Secondary Brakes
Are fully modulated and the front and rear service brake circuits are isolated so one circuit can operate if pressure drops int he other circuit.

Cooling System
Works with the engine to meet emissions standards as well as improve serviceability and reduce downtime.


Advanced Modular Cooling System (AMOCS) with Air-to-Air Aftercooling System (ATAAC)
In order to meet EPA Tier 2 and EU stage II emissions requirements for the Year 2002, the software for the Cat 3412 HEUI engine has been changed and the cooling system upgraded to an AMOCS that utilizes the ATAAC system to achieve lower particulate, NOx and sound output. The proven AMOCS system is currently used on other Caterpillar models such as the 834G, 854G, 988G and 992G and with ATAAC technology effective with the 834G and 988G introduction.

ATAAC System
Provides a separate cooling system for the intake manifold air complementing the engine jacket water cooling system. The ATAAC system routes hot, compressed air from the turbo and cools it with a single pass, air-to-air aluminum heat exchanger. The cooled compressed air is then delivered to the engine intake manifold. Providing the engine with cool compressed air greatly reduces the emissions produced, meeting Tier 2 requirements for a cleaner environment.

Separated Cooling System
Isolates the AMOCS radiator and demand fan from the engine compartment with a shield allowing the radiator to receive outside ambient air through the side and top vents at a much lower temperature than the hot air from the engine compartment. This improves the system’s efficiency and allows the radiator size to be decreased and the rear hood to be sloped, improving the rear viewing area. Also, sound levels are reduced due to the lower fan speed of a more efficient cooling system.

AMOCS
Is a Caterpillar exclusive technology that improves serviceability and increases cooling efficiency by 22 percent. Ambient working temperature for the standard 844 is 43° Celsius (110° Fahrenheit). A high ambient cooling package with a 50° Celsius (122° Fahrenheit) capacity is available as an attachment.

Serviceability
Is a key benefit. Tubes are welded to a large, thick header, providing the strength of the tube-to-header joint that reduces the possibility of coolant leaks. The AMOCS modular core design allows removal of a single core without removing the entire radiator - reducing downtime through ease of serviceability. Replacing the individual core also reduces repair costs.

Two Pass System
Offers increased cooling capacity. Coolant travels from the engine to the fan side of the bottom tank, up the fan side of each core, over the top, down the engine side of the core, into the engine side of the bottom tank and back to the engine. The improved flow pattern allows the coolant to pass through the radiator twice for better cooling. The AMOCS design improves serviceability, reduces downtime and increases cooling capability.

Structures
Advanced design and materials provide superior strength.


Structures

Structure Welds
Are more than 90 percent robotically welded. This provides highly consistent welds with deep plate penetration and excellent plate fusion. The benefit is greater fatigue strength and longer life than with conventional welding methods.

Castings
In the engine end-frame are used in critical high-stress areas to help spread the load and reduce the number of parts. The casting for the rear trunnion mount also serves as an engine mount, which provides a load path for the weight and torque of the engine to travel down to the trunnion and then on through to the axle. Other castings used in the engine-end frame include: front trunnion mounts, steering cylinder brackets, articulation stops and lock link.

1 Box-Section Rear Frame
Absorbs shock loads and torsional forces, solidly maintaining alignment for hitch pins and driveline.

2 Four-Plate Front Frame
Provides maximum structural strength to resist twisting loads during dozing applications.

3 Upper and Lower Hitch Pins
Pivot on double-tapered roller bearings and are shaped to direct stress away from the end of the weld, resulting in a smoother transition of stress loads.

4 Spread-Hitch Design
Helps square up the frame and provides more clearance for hydraulic lines. Double tapered roller bearings and hardened pins resist both horizontal and vertical loads to increase life. The spread hitch also makes service access easier.

Engine and Transmission Mounts
Are designed to use mushroom and cup-shaped ISO mounts, reducing component vibration and sound levels. The engine mounts directly to the rear cross member, simplifying and improving load transfer structure.

Hydraulics
Well-balanced hydraulics deliver precise low-effort control and trouble-free operation.


Hydraulics

1 Two Separate, Hydraulic Systems
One for lift/tilt/tip and brakes, while the other is for steering and the hydraulically-driven engine cooling fan. Benefits of two systems are increased cooling and elimination of cross-contamination. If one system runs hot or is contaminated, the other will be unaffected.

2 Blade Control
Floor-mounted control lever sends signals to a pilot valve for tilt/tip control and a main valve for lift control.
  • Caterpillar built tandem vane pumps provide hydraulic flow for the lift, tilt and tip functions. The circuit is well balanced to provide control when all functions are used simultaneously.
  • Well-proven pumps, valves and cylinders are common with those used on Caterpillar large track-type tractors.
  • For improved serviceability, all hydraulic pumps are mounted on a single pump drive.

3 Load Sensing Steering with STIC Control System
Is a revolutionary system that integrates steering and transmission into a single controller. The variable displacement pump maximizes machine performance by directing power through the steering system only when needed. More efficient use of power results in decreased fuel consumption and higher production.
  • Simple side-to-side motions of the stick turn the machine right or left offering a 35 degree steering angle in both directions. Center-point frame articulation allows the front and rear wheels to track.
  • Transmission shifting forward, neutral or reverse is controlled by the operator’s fingers and gear selection is controlled by the operator’s thumb.

XT-3 and XT-5 Hose
O-ring face seals and large-bore lift and tilt cylinders top off the hydraulic system, delivering the performance and durability owners expect. Reliable components reduce leaks and help protect the environment.

Hydrostatic Cooling Fan
Is used for engine, transmission and hydraulic cooling. A variable displacement pump drives the fan’s hydraulic motor so that fan speed varies with coolant temperature. The fan draws only the power needed for cooling, reducing fuel consumption and increasing efficiency.

Blades and Blade Controls
Caterpillar blades are built to handle tough applications and well-proven Cat components deliver dependable service and ease of operation.


Blades and Blade Controls

Caterpillar Blades
Are designed with excellent dozing and rolling characteristics.
  • Capacities and widths are set to achieve increased productivity.
  • Special design allows for spreading of cover material as well as dozing of heavier loads.
  • High-strength, pressed rib construction.
  • Caterpillar large track-type tractor bolt-on cutting edges and bottom wear plates.
  • Fitted with Caterpillar standard hardware and Ground Engaging Tools (GET).
  • Rebuildable for long blade life.

Coal Blade
Is designed for precise and productive dozing while helping to retain load control with increased capacity for lighter materials. Wing angles help retain the load while dozing.

Semi-U Blade
Combines the characteristics of the S and U blades into one package. Provides increased capacity with the addition of short wings which include only the dozer end bits without sacrificing spreading characteristics of straight blades.

Heavy-Duty Semi-U Blade
Has the same configuration as the semi-U blade but is built with thicker plates for more severe applications.

Heavy-Duty Blade Linkage
Is common with a Caterpillar D9 Track-Type Tractor. These well-proven components are designed for tough applications.
  • Lift cylinders raise and lower blade for efficient dozing action.
  • Two position tilt cylinder mounting for increased flexibility for various applications.
  • Cutting edges are DH-2 steel. End bits are DH-3 to provide maximum
  • Trunnions, pusharms and tag link are sized for large dozing loads.

Single-Lever Blade Control
Hydraulically operates blade raise, lower, tilt and tip.

Lift Circuit
Features four positions: raise, hold, lower and float with detente hold on float.

Tilt/Tip Circuit
Offers operator selected single or dual-tilt and fingertip control for tip operation.

Low-Effort Control
Comes from the single-lever lift/tilt/tip control that is floor mounted and cable actuated with pressure compensation for tilt/tip.

Single or Dual-Tilt Operation
Can be selected by the operator by using a switch located on top of control lever. A generous range of tilt motion enables excellent control for dozing.

Operator Station
Comfort and control — a top quality operator station helps maximize productivity.


Operator Station

Cab Design
Is spacious and incorporates innovations for operator comfort and productivity, include an excellent viewing area, interior sound levels below 75 dB(A), Caterpillar Comfort Series seat, standard coat hook, cup holder, storage bin, sun visor and intermittent wet-arm wipers. It is also radio-ready for two-way radios.

1 STIC Control System
Is a revolutionary system that integrates steering and transmission into a single controller. Simple side-to-side motions of the operator’s left arm turn the machine right or left. Transmission shifting forward, neutral or reverse is controlled by the operator’s fingers, and gear selection is controlled by the operator’s thumb. These factors combine to produce a fluid motion that reduces effort and allows the operator to work the machine for long periods of time with little or no fatigue.

2 Left Pedal
Operates the Impeller Clutch Torque Converter for about the first inch of travel, then engages the brakes. Within the first inch of pedal travel, rimpull can be controlled from 100 percent to 20 percent.

3 Comfort Series Seat
With air suspension and retractable seat belt is designed for comfort and support. Seat cushions reduce pressure on the lower back and thighs while allowing unrestricted arm and leg movement. The seat has three height levels. The retractable seat belt remains off the floor and is easy for the operator to reach.

4 Quick-Shift Feature
Allows quicker cycle times by shifting from first forward to second reverse.

5 Throttle Lock
Allows the operator to preset the engine speed and concentrate on productivity. The throttle lock can be deactivated by pressing the brake pedal.

6 Electronic Monitoring System III (EMS III)
Continually monitors various machine systems through three instrument clusters and provides a three-level warning system to alert the operator of immediate or pending problems. EMS III shares information with the engine, hydraulic and transmission controls that can be used during servicing to simplify service and troubleshooting.
  • Gauges Display engine coolant, transmission oil and hydraulic oil temperatures, engine oil pressure and fuel tank level.
  • Tachometer/Speedometer Display engine speed and gear indicator
  • Alert Indicators
Include charging system, parking/secondary brake, supplemental steering, brake oil pressure, engine coolant flow and transmission filter status.

7 Floor-Mounted Hydraulic Blade Controls
Are adjustable fore and aft, with a height-adjustable armrest so operators of any size can find a comfortable operating position. A single lever control allows operator to control blade functions: lift/lower, tip and tilt. The switch control on top of control lever allows option of single or dual-tilt operation.

8 Torque Converter Lock-up Clutch
Is activated when the operator presses a switch on the console. The 844 automatically shifts from torque converter drive to direct drive when a set speed in second and third forward or all gears in reverse is reached, providing faster travel speeds and less fuel consumption.

Large, Viewing Area
Enhances viewing in all directions. Bonded glass in the front window eliminates distracting metal frames with the best operator visibility to the blade.

Serviceability
Less time spent on maintenance means more time on the job.


Serviceability

Easy Maintenance
In addition to the servicing features built into the engine, the 844 includes:

• Rear Access Stairs
For easy, comfortable access for operators and service personnel.

• Large Engine Access Doors
Provide excellent access to service points, engine oil dipstick, diagnostic connector, engine oil and fuel filters, starting receptacle, air filter indicator, air filters, fuel/water separator and the ether starting aid cartridge.

• Large Service Platform
Provides passage to hydraulic filter, fuel fill and transmission filters through easy-to-open doors.

• Large Door
Provides entrance to transmission and pumps when service is required.

• Large Platform Door
Provides access to fuses and electronic control modules.

• Batteries
Are accessible through hinged doors in bumper.

• Side Access Doors
On the radiator guard provide easy access for radiator cleanout.

• Grouped and Labeled Lube Points
Accessible at ground level, make daily lube maintenance quick and easy.

• Sight Gauges
In the hydraulic tanks and radiator provide quick check for fluid levels.

Complete Customer Support
Cat Dealer services help keep machines operating longer with lower costs.


Complete Customer Support

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

Purchase
Look past initial price. Consider the financing options available as well as the 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 the customer’s investment.

Product Support
You will find nearly all parts out our dealer parts counter. Cat dealers use a worldwide computer network to find in-stock parts to minimize machine downtime. Save money with genuine Cat Reman parts. You receive the same warranty and reliability as new products at cost savings of 40 to 70 percent.

Operation
Improving operating techniques can boost your profits. Your Cat Dealer has training videotapes, literature and other ideas to help you increase productivity.

Maintenance Services
Choose from your dealer’s range of maintenance services when you purchase your machine. Repair option programs guarantee the cost of repairs up front. Diagnostic programs such as S*O*SSM and Coolant Sampling and Technical Analysis help you avoid unscheduled repairs.

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

EQUIPMENT
Standard Equipment

Electrical
  • Alternator, 100-ampere
  • Converter, for 12-volt accessories
  • Diagnostic connector for starting and charging systems
  • Electric starter (heavy-duty)
  • Electrical system, 24-volt
  • External lighting system, front and rear
  • Maintenance-free batteries
  • Starting receptacle for emergency starting
Operator environment
  • Air conditioner, R-134A refrigerant
  • Contour Series Seat with air suspension
  • Cigar lighter and ashtray
  • Coat hook
  • Computerized Monitoring System
  • Dome light (cab)
  • Electric horn
  • External two-post ROPS structure
  • Heater and defroster
  • Load-sensing steering
  • Quick-shift feature
  • Radio-ready cab for entertainment or two-way radio (three-point mounting)
  • Rearview mirrors (interior and exterior mounted)
  • Retractable seat belt 76 mm (3 in) wide
  • ROPS cab with sound suppression
  • Floor mounted hydraulic controls
  • Sight gauges, hydraulic oil and engine coolant
  • Single-lever blade control
  • STIC Control System
  • Storage for lunch box, cup
  • Sunshade/visor, front and rear
  • Throttle lock
  • Tinted glass
  • Transmission gear indicator
  • Wet-arm wiper/washers, front and rear
Power train
  • Cat 3412E HEUI engine
  • Fuel priming aid
  • Brakes: Parking: Dry, multi-disc brake; transmission mounted,
  • Impeller Clutch Torque Converter with lockup clutch
  • Precleaner/ejector
  • Remote-mounted hydraulic engine fan
  • Separated cooling system
  • Sound suppressed muffler
  • Supplemental steering
  • Swing-out cooler cores
  • Transmission,
Other standard equipment
  • Backup alarm
  • Cold weather starting system
  • Drawbar hitch with pin
  • Fenders (front)
  • High speed oil change system
  • Hydraulic oil cooler
  • Muffler
  • Lighting, general purpose (four)
  • Locking engine enclosures
  • Power train/guard
  • Rear access stairs
  • Vandalism protection and caplocks
  • Venturi stacks
Tires
  • 45/65 R39 L-4 (XLDDIA), Michelin


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