Service Training SESV1717Meeting Guide 717 November 1999

TECHNICAL PRESENTATION

924G/924Gz WHEEL LOADERS

INTRODUCTION

924G/924GZ WHEEL LOADERSINTRODUCTION

MEETING GUIDE 717 SLIDES AND SCRIPT

AUDIENCE

Level II--Service personnel who understand the principles of machine systems operation, diagnosticequipment, and procedures for testing and adjusting.

CONTENT

This presentation describes the significant changes from the 924F/IT24F in machine features andsystems. This presentation covers component locations, nomenclature and a brief description ofsystems operation.

OBJECTIVES

After learning the information in this presentation, the serviceman will be able to:

1. identify the major changes in the machine features and systems;2. explain the basic operation of each system;3. locate and identify components; and4. explain the function of the components and systems.

REFERENCES

924G/924Gz Wheel Loader Service Manual RENR3500924G/924Gz Wheel Loader Parts Manual SEBP2974

PREREQUISITES

Interactive Video Course "Fundamentals of Mobile Hydraulics" (CD ROM) TEMV9001STMG 546 "Graphic Fluid Power Symbols" SESV1546

SUPPLEMENTARY TRAINING MATERIAL

STMG 684 "928G Wheel Loader/IT28G Integrated Toolcarrier--Introduction" SESV1694STMG 670 "914G Wheel Loader/IT14G Integrated Toolcarrier--Introduction" SESV1670STMG 581 "910E/916F/IT12B/IT14B Power Shift Transmission" SESV1581STMG 667 "Challenger 35/45/55 Agricultural Tractors--Implement, Hitch and Steering Systems" SESV1667

Estimated Time: 1.5 HoursVisuals: 61 (2 X 2) SlidesServiceman Handouts: 3 Work SheetsForm: SESV1717Date: 10/99

© 1999 Caterpillar Inc.

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TABLE OF CONTENTS

INTRODUCTION ..................................................................................................................5

MACHINE CONFIGURATIONS ..........................................................................................6924G..................................................................................................................................7924Gz................................................................................................................................8

MACHINE APPEARANCE...................................................................................................9

OPERATORÕS STATION.....................................................................................................10

ENGINE AND ELECTRICAL SYSTEM............................................................................21

POWER TRAIN ...................................................................................................................28Torque Converter and Transmission ...............................................................................29Power Train Hydraulic System.......................................................................................31Electronic Transmission Control System........................................................................36Axles ...............................................................................................................................39

HYDRAULIC SYSTEMS....................................................................................................42Work Tool Hydraulic System..........................................................................................44Steering System ..............................................................................................................65Brake/Fan Drive System.................................................................................................70

CONCLUSION.....................................................................................................................75

SLIDE LIST..........................................................................................................................76

SERVICEMAN'S HANDOUTS...........................................................................................77

INSTRUCTOR NOTES

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¥ Explain coverage

1

INTRODUCTION

This presentation covers the 924G and the 924Gz Wheel Loaders. ACaterpillar 3056T direct injection, turbocharged engine provides 87 kW(116 hp) to the flywheel at 2300 rpm for the 924G and the 924Gz.

An electronically controlled, four-speed forward, three-speed reverseautoshift transmission of countershaft design with a single stage torqueconverter transfers the engine power to the axles. The power train issimilar to that on the 924F and the IT24F.

The 924G/924Gz use a parallel flow work tool hydraulic system withclosed center, pilot operated control valves and a load sensing, variableflow, axial piston pump. The 924F/IT24F machines use an interruptedseries flow hydraulic system with open center, pilot operated controlvalves and a fixed displacement pump.

The 924G/924Gz load sensing steering system uses a variabledisplacement pump, as did the 924G/IT24F.

The brake and fan drive hydraulic system has been redesigned, howeverthis system is similar to that on the 928G wheel loader and the IT28Gintegrated tool carrier.

This presentation will cover machine orientation and the operation of thepower train and machine hydraulic systems for the 924G and the 924Gz.

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924G/924Gz WHEEL LOADERS

© 1999 Caterpillar Inc.

¥ Power train

¥ Work tool hydraulics

¥ Steering system

¥ Brake/fan drivesystem

¥ MachineConfigurations

2

MACHINE CONFIGURATIONS

The 924G replaces both the 924F and the IT24F. The 924G combines theversatility of an integrated toolcarrier with the production of a wheelloader. Therefore, an integrated toolcarrier configuration is not necessaryfor this G series update.

The 924Gz retains the Z-bar linkage to satisfy market needs for areas thatstill require this configuration

Both the 924G and the 924Gz machines are wheel loaders.

The only systems that are different between the 924G and the 924Gz arethe work tool hydraulic systems and the machine structures.

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3

¥ 924G 924G Wheel Loader

The 924G is equipped with Versa Link© linkage for controlling the tilt ofthe bucket or tool. This linkage includes a box boom lift arm (1). Thebox boom lift arm offers the operator better visibility to the bucket or tool.A High Lift linkage option enhances the loading capability of the 924G byallowing the machine to load taller trucks.

A hydraulically controlled work tool coupler (2) is an option on the 924G.This coupler is the same interface as previous integrated toolcarriers andwill connect to existing Caterpillar work tools.

The main difference between the work tool hydraulic systems of the 924Gand the 924Gz is in the tilt control valve (3). The 924G tilt control valveregenerates the return oil from the tilt cylinder during the dump cycle.The tilt control valve equalizes the pressure on both sides of the piston inthe tilt control cylinder with the pressure in the lift circuit during the dumpoperation. Hydraulic system operation will be discussed in greater detaillater in this presentation.

924G Configuration

BOOM

COUPLER

Versa Link linkage with box boomlift arm

Hydraulically controlled coupler

WORK TOOLHYDRAULICS

Regeneration and equalization ofpressure by tilt control valve

2

1

33

3. Tilt control valve

2. Hydraulicallycontrolled coupler

1. Box boom lift arm

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4

¥ 924Gz 924Gz Wheel Loader

The 924Gz is equipped with Z-bar linkage for controlling the tilt of thebucket. This linkage includes a conventional slab-type lift arm (1).

The 924Gz can be equipped with a Caterpillar work tool coupler as anaftermarket attachment. However, these machines will be delivered onlywith pin-on linkage (2).

The 924Gz tilt control valve (3) does not regenerate oil or equalizepressure during the dump cycle.

924Gz Configuration

BOOM

COUPLER

Z-Bar linkage

Can be equipped withCaterpillar work tool coupler

WORK TOOLHYDRAULICS

Conventional tilt control valveoperation

2

1

3

3. Tilt control valve

2. Pin-on linkage

1. Lift arms

¥ Redesigned cab

5

MACHINE APPEARANCE

The redesigned cab and sloped hood visually differentiate the924G/924Gz from the 924F Wheel Loaders and the IT24F IntegratedToolcarriers.

The cab is equipped with two doors for easier access. Improved ladders,handrails and platforms make entry and exit easier and offer room tomaneuver while servicing the machine.

The sloping rear hood enhances the operator's view toward the rear of themachine. The rear hood configuration allows the operator to see objectsclose to the rear of the machine that cannot be seen with the rectangularshaped hood found on the previous "F" Series Wheel Loaders.

The 924G/924Gz is also larger in size than the 924F Wheel Loaders andthe IT24F Integrated Toolcarriers. The 924G/924Gz is 14 mm (0.5 in.)taller and it has a 100 mm (4 in.) longer wheel base than the 924F/IT24F.

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¥ Larger

¥ Sloping hood

- Access doors

- Handrails

¥ Cab components:

- Right side door

- Bonded glass

6

OPERATOR'S STATION

The 924G/924Gz cab is shared with the 928G and the IT28G. The twodoor design provides access from the right or left side of the cab.

The bonded glass in the front window eliminates distracting metal frames.The increase in cab glass area enhances the view around the machine.

Molded nonmetallic materials inside the cab allow for easy installation offeatures such as a coat hook, lockable storage boxes, and cup, vacuumbottle and cooler holders.

Improved ventilation provides better air flow to the operator and thewindows. The optional air conditioning keeps the cab temperaturecomfortable for operation in warm environments.

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¥ Improved ventilation

¥ Molded nonmetallicmaterials

¥ Door latch release(arrow)

7

Both doors have latches that hold the doors fully open.

Push the button at the pivot point of the door in order to release this latch.

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¥ Cab components:

1. Adjustable seat

2. Seat cushion anglelever

3. Front/rear lever

4. Suspensionadjustment knob

5. Retractable seatbelt

8

The six-way adjustable suspension seat (1) adds to the overall comfortlevel by smoothing the ride over rough ground.

The seat cushion angle lever (2) raises the front of the seat cushion to thedesired position.

The front/rear lever (3) allows forward and rearward adjustment.

The suspension adjustment knob (4) adjusts the stiffness of the seatsuspension.

The backrest adjustment (not shown) allows the backrest centerline toconform to the operator's spinal curve and provides the proper support tothe back's lumbar region.

A retractable seat belt (5) is also included with the seat.

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2

1 5

2

3

4

¥ Left front console

1. Five positionheadlamp switch

2. Rotating beaconswitch

3. Thermal start aidswitch

4. Transmissionneutralizer override

9

A left front console has been added to the 924G/924Gz operatorÕs station.Some controls have been moved here for easy access by the operator.

The headlamp switch (1) has the following positions: OFF, PARK(panel/tail lamps), ROADING (front headlamps), WORK 1 (front cabfloodlamps) and WORK 2 (rear cab floodlamps). Each position of theswitch illuminates more lamps than the previous positions.

The three switches below the headlamp switch include: rotating beacon(2), thermal starting aid (3) and the transmission neutralizer override (4).

During normal operation, the transmission is neutralized when the brakesare applied. Use the transmission neutralizer override switch to overridethis feature.

Warning lamps are located on the left front console, including the brakepressure indicator lamp, engine oil pressure indicator lamp, coolanttemperature indicator lamp, transmission oil temperature indicator lampand differential lockup indicator lamp.

NOTE: Throughout the cab, some of the switches are for optionalattachments, so not every machine will have all the switches that areshown in this presentation.

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1

3 2

4

¥ Front console

1. Horn button

2. Lamps

3. Engine coolanttemperature gauge

4. Hydraulic oiltemperature gauge

5. Fuel level gauge

6. Transmission oiltemperature gauge

10

In the center console, individual gauges with dial faces show theconditions of the various machine systems. The group includes thefollowing gauges: engine coolant temperature (3), hydraulic oiltemperature (4), fuel level (5), and transmission oil temperature (6). Anoptional speedometer (not shown) is available. This gauge group issimilar to the gauge group in the cab of the 928G/IT28G.

The horn button (1) is located in the center of the steering wheel.

The four lamps (2) spaced around the steering column are the turn signalindicators (left and right), the high beam indicator (optional) and thetrailer light indicator (optional). The F-N-R indicator is located directlyabove the steering column.

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12

3

4

55

6

- 15 -

¥ Right front consolecomponents:

1. Turn signal(optional)

2. Engine start switch

3. Dimmer switchlocation (optional)

4. Lighter (24V)

5. Secondary steeringtest switch(optional)

6. Indicator lamps

7. Steering wheel tiltlatch

8. Front windshieldwiper switch

9. Rear windshieldwiper switch

11

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7

12

4

59

6

3 9

Shown in this view is the right side of the front console.

The optional turn signal lever (1) is on the right side of the steeringcolumn. Pulling the turn signal switch away from the console operatesthe hazard lights.

The engine start switch (2) is located on the right side of the frontconsole.

A switch for dimming the roading lights (3) is optional.

A cigarette lighter (4) on the right front console provides a 24V powersource for electrical components. An optional 12V power source islocated on the lower left side of the seat.

The switch to activate the secondary steering system test (5) is locatednext to the indicator lamps.

Indicator lamps (6) include: alternator, park brake, cab floodlamps, and(if equipped) secondary steering motor ON lamp and a primary steeringpressure fault lamp.

The steering wheel tilt latch (7) allows the operator to adjust the steeringwheel to the desired angle.

Two switches are used to control the windshield wipers. One switch (8)controls the front windshield wiper and another switch (9) controls therear windshield wiper.

¥ Lever functions:

1. Joystick control

2. Transmissioncontrol switch

3. Third functioncontrol

4. Fourth functioncontrol

12

Reduced lever efforts and shorter lever throws are achieved by using pilotoperated work tool controls resulting in decreased operator fatigue.

The 924G/924Gz will have one of several different work tool hydrauliccontrol arrangements depending on the machine configuration. Thestandard configuration has a joystick pilot valve control lever (1). Thejoystick pilot valve control lever controls the bucket LIFT and DUMPfunctions. Additional control levers are used to control the third (3) andfourth (4) functions if the machine is so equipped. Some machines maybe equipped with as many as four single function levers. However, theHigh Lift option will only allow for three functions.

The pilot valves contain normally energized solenoids which hold thelever in detent for the loader FLOAT position, the bucket kickout circuit,the loader lift kickout circuit, or the third function lever "rearwardposition."

A hydraulic control lock (pilot shutoff) lever is located between the seatand the right console. The lever controls a valve which interrupts theflow of oil to the pilot valves and also deactivates the control leversolenoid detents if moved out of the unlocked position. Fully raise thelever in order to shut off the pilot system. The lever should be all the wayon or off, do not leave the lever in the middle position.

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1

2

3 4

¥ Solenoids performdetent

¥ Hydraulic control lock

The hydraulic control lock lever can be used to prevent a work tool frommoving accidentally when maintenance is being performed or to preventaccidental movement of the work tools during roading.

A transmission control (F-N-R) switch (2) can be incorporated into thejoystick pilot valve control lever. This switch allows the operator to shiftfrom forward to reverse without releasing the steering wheel.

An optional downshift switch (not shown) is located at the front of thejoystick pilot valve control lever.

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¥ Right consoleswitches

1. Fan speed switch

2. Temperaturecontrol knob

3. Autoshift ON/OFF

4. Ride controlON/OFF/AUTO

5. Kickout ON/OFF

6. Defrost ON/OFF

7. Air conditioningON/OFF

8. Coupler controlswitch

13

Shown in this view is the right side console. Switches mounted on theconsole are used to control certain machine functions. The icon on theswitch indicates the function that the switch performs. This locationprovides better accessibility to these controls. Controls that are located onthe right console are autoshift on/off (3), ride control on/off/auto (4),kickout on/off (5), defrost on/off (6), air conditioning (7), temperaturecontrol (2) and fan speed switch (1).

A switch (8) controls the engagement and disengagement of the coupleron the 924G. Two actions are required to activate the switch. First, theslide on the switch must be moved forward, then the switch can beactivated. This prevents inadvertent decoupling of the work tool. Thesteering system supplies oil to the control valve for the coupler.

The fan speed switch controls the heating and air conditioning fan speed.The temperature control knob allows the operator to vary the airtemperature from the heating and air conditioning systems.

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1

2

3

4

5

6

7

8

¥ Pedals

1. Accelerator

2. Service brakepedals

14

The brake pedals have changed to a suspended pedal from a clip pedal onthe 924F/IT24F.

The pedal (1) on the right is the accelerator. The center pedal and thepedal on the left (2) are both service brake pedals. Linkage connects thebrake pedals. Depressing either pedal ENGAGES the service brakes andNEUTRALIZES the transmission unless the transmission neutralizeroverride switch is activated.

The transmission neutralizer is controlled by two pressure switches on thebrake control valve.

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1

2

¥ Side console

1. Fuses

2. ET Connector

3. Relays

15

All the fuses (1) are located in the operatorÕs station inside the right sidedoor. This helps protect the fuses from outside elements and provideseasier access to the fuses.

A diagnostic indicator lamp is located at the bottom of the fusecompartment. The diagnostic indicator lamp can be used to identifyactive and logged faults.

The diagnostic port connector (2) for electronic technician is located justinside the right door of the cab.

Several relays (3) are located on this panel: Alarm "A" relay, Alarm "B"relay, Park brake light/Seat alarm relay, Park brake alarm relay, Ridecontrol/Load check relay, and the backup alarm relay.

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1

3

2

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16

¥ 3056 Engine

1. Engine oil filters

2. Tool box

3. Fuel tank

4. Fuel fill tube

5. Battery disconnectswitch

6. Engine oil S¥O¥Sport

ENGINE AND ELECTRICAL SYSTEM

The engine is mounted in the rear frame. Doors on each side of themachine allow access to the engine compartment.

The engine in the 924G/924Gz is a Caterpillar 3056T, producing 87 kW(116 hp) to the flywheel, which is a 10% increase in power over the924F/IT24F. The 3056T will meet the vehicular emissions regulationsthrough the year 2002.

The engine oil filters (1), which have internal check valves to prevent oilleakage during filter changes, are located on the left side of the engine.

The fuel tank (3) is located at the rear of the machine below the coolingsystem. The non-metallic tank prevents fabrication debris and corrosionand is more resistant to leakage. A tool box (2) is located directly abovethe fuel tank.

1

4

2

3

5

6

7

8

7. Fuel injectionpump

8. Fuel-waterseparator

The fuel fill tube (4) can be accessed with the radiator closed and the rightside door open.

The battery disconnect switch (5) is also located on the right side of themachine. The engine oil S¥O¥S port (6) is located on the right side of theengine.

The fuel-water separator (8) is located on the right side of the machine.The 924F/IT24F did not have a fuel-water separator.

The 3056T engine has a different fuel injection pump (7) and differentinjectors than the 3114 engine. The fuel system configuration in the924G/924Gz is similar to the current fuel system configuration on the914G/IT14G.

INSTRUCTOR NOTE: For additional information about the fuelsystem, see STMG 670 "914G Wheel Loader/IT14G IntegratedToolcarrier" (Form SESV1670).

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¥ Cooling system

1. Fan drive motor

2. Fan and fan shroud

3. Air conditioningcondenser

4. Hydraulic oil cooler

5. Radiator

The 924G/924Gz cooling system is different from that on the 924F/IT24F.The standard cooling system can be used in a wider variety of applicationslike waste handling, agricultural applications and landfill operations.

The non-metallic fan pulls the air through the radiator. The incoming airflows through the screens in the engine compartment access doors. Thesescreens have a vertical weave in order to allow foreign material to dropoff the screen when the machine is not operating.

The fan is driven by a hydraulic motor (1), allowing the fan and the fanshroud (2) to be swung away from the radiator. A gear pump, which isshared with the brake system, provides the oil flow which drives the fandrive motor.

The hydraulic oil cooler (4) and the air conditioning condenser (3) are atthe front of the radiator and can be swung forward to clean the radiator.

The standard hydraulic oil cooler is included in the package with anoptional heavy duty hydraulic oil cooler.

2 5

1

3

4

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18

¥ Starting system

This slide shows the wiring schematic for the starting and charging systemin the RUN condition.

The red colored wires have battery voltage when the key start switch is inthe OFF position. When the key is moved to the "ON" or "START"positions, power flows from the batteries through the auxiliary breaker tothe "B"terminal of the key start switch.

Power flows from the "R" terminal on the key start switch through thefuel shutoff resistor to the fuel shutoff solenoid. When the solenoid isenergized, the fuel is allowed to enter the fuel injection pump. If the keyis moved to the "OFF" position or if there is a loss of electrical power, thesolenoid becomes de-energized and the flow of fuel to the pump isinterrupted.

COOLANTSWITCH

T°

399-OR

DISCONNECTSWITCH

(OPTIONAL)

RESISTOR

396-PK-18

377-OR

310-PU

RESISTOR

START AIDSWITCH

FROMLAMP

SWITCH

FUELSHUTOFFSOLENOID

10 A115-RD

G S

MOTOR

MTR BAT

CST SHIFTER

FIRST GEARSECOND GEARTHIRD GEARFOURTH GEARSTART RELAYNEUTRALREVERSEFORWARD

+ BATTERYGROUNDEXTERNAL FWDEXTERNAL REVBACKUP REALYKEY SWITCH IN

STARTRELAY

STARTER

RD-00

105-RD

307-OR

304-WH

109-RD

306-GN

B-

B+

D+

109-RD

MAINRELAY

ALTERNATOR

KEY STARTSWITCH

308-YL

117-RD

R

C

S

B ST

OFF

ON

ALT. BREAKER

101-RD

30

60

60

109-RD

MAIN BREAKER

109-RD

AUX. BREAKER

115-RD

LAMP BREAKER

15

R

924G STARTING AND CHARGING SYSTEM

POSNEGPOSNEG

15 A

COLDSTART

ADVANCEMOTOR

MOTOR

TO SERVICE METER ANDSECONDARY STEERING CONTROL

188-WH

102-RD

112-PU

373-GN

COLD STARTHEATER

Power also flows from the key start switch, to the transmission controllever (CST shifter). If the lever is in the neutral position, power will flowthrough the shifter to the start relay.

When the start relay is energized, power flows from the batteries, throughthe alternator breaker and the start relay, to the starter.

The optional start aid system includes the following components: thefifteen amp fuse, start aid switch, cold start resistor, cold start heater,coolant switch and the cold start advance motor. When the key is in the"ON" position, the main relay is energized which connects the cold startsystem to the batteries.

The charging system includes the following components: the batteries,alternator breaker, alternator and the key start switch.

The "R" terminal on the key start switch provides the "exciting" current tothe alternator in order to energize the electro-magnets in the alternator.As the alternator turns, power flows through the alternator breaker tocharge the batteries. Power from the alternator also flows through themain breaker and the main relay to the accessories.

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¥ Optional start aidsystem

¥ Charging system

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19

1. Start relay

2. Cold start resistor

3. Fuel shutoffresistor

4. Main breaker

5. Alternator breaker

6. Auxiliary breaker

7. Starter

8. Cold start heater

9. Alternator

Shown in this slide are the major electronic components on the left side ofthe machine.

The breaker/relay panel is attached to the left side of the hydraulic tank.Included on this panel are the start relay (1), the cold start resistor (2), thefuel shutoff resistor (3), the main breaker (4), the alternator breaker (5),and the auxiliary breaker(6).

The starter (7) is located at the front of the engine compartment on the leftside.

The alternator (9) is located at the rear of the engine compartment on theleft side. There is a standard alternator and an optional high outputalternator.

The cold start heater (8) is also located at the rear of the engine.

2

3

1

4

5

7

6

5

4

9

8

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20

1. Transmissioncontrol lever

2. Main relay

3. Fuel shutoffsolenoid

4. Battery

Shown in this slide are the major elecrical components in the cab and onthe right side of the machine.

The transmission control lever (CST shifter) (1) is located on the steeringcolumn.

The main relay (2) is located below the fuse panel inside the cab rightdoor.

The fuel shutoff solenoid (3) is on the top of the fuel injection pump.

One battery (4) is located on each side of the machine in an enclosedbattery box.

1

3

2

4

21

POWER TRAIN

The power train for the 924G/924Gz is very similar to that of the924F/IT24F.

The transmission is the same transmission that is used in the 924F/IT24F.

The axles use a larger casting. A new mounting of the front axle to thefront frame provides a more rigid structure to the machine. An integratedlip was added to the casting to protect the Duo Cone seals in wastehandling applications.

The differential and the inboard final drives are the same as those on the924F/IT24F.

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¥ Transmission

¥ Axles

¥ Final drives

¥ Differential

¥ Torque converter

- Automotive style

- Flex plate

22

Torque Converter and Transmission

One of the changes in the power train is the torque converter.

The torque converter on this machine is a automotive type torqueconverter, similar to those used on other small Caterpillar machines.

A flex plate is used on the 924G/924Gz to connect the engine and thetorque converter.

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23

¥ Same transmission as924F/IT24F

- Torque converter

- Power train pump

- Input shaft

- FORWARDHIGH/LOW shaft

- REVERSE andSECOND shaft

- THIRD and FIRSTshaft

- Output shaft

- Parking brake

PUMPTORQUE

CONVERTER

INPUT SHAFT

LOW AND HIGHCLUTCH SHAFT

REVERSE AND SECONDCLUTCH SHAFT

THIRD AND FIRSTCLUTCH SHAFT

OUTPUT SHAFT

PARKING BRAKE

924G/924Gz TRANSMISSION

The power shift transmission (countershaft design) provides fourFORWARD speeds and three REVERSE speeds. This is the sametransmission that is used in the 924F and the IT24F.

The gear-type transmission pump provides oil flow to the transmissioncontrol valve and transmission speed and directional clutches.

The transmission has five shafts. The input shaft is driven by the turbineof the torque converter. The FORWARD LOW and FORWARD HIGHclutch shaft and the REVERSE and SECOND clutch shaft are then drivenby the input shaft. The third clutch shaft contains the THIRD and FIRSTgear speed clutches. The output shaft directs power to the front and rearaxles. The shoe-type parking brake is mounted on the transmission outputshaft.

INSTRUCTOR NOTE: For additional information about thetransmission, see STMG 581 "910E/916F/IT12B/IT14B Power ShiftTransmission" (Form SESV1581).

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24

¥ Identify componentsand trace oil flow

PUMP

FILTER

FLOWCONTROL

VALVE

CHECKVALVE

RELIEFVALVE

TORQUECONVERTER

COOLER

TRANSMISSIONLUBE

3

5

12

4

SUCTIONSCREEN

DIFFERENTIALVALVE

1 3

4 5

2

CONTROLVALVE

6

DUMPVALVE

6

924G/924Gz POWER TRAIN HYDRAULIC SYSTEM

Power Train Hydraulic System

The power train hydraulic system on the 924G/924Gz is the same as thepower train hydraulic system on the 924F/IT24F.

The gear pump is driven by the torque converter impeller through atransfer gear. The filter is externally mounted.

The flow control valve is mounted in the transmission case. The flowcontrol valve sends oil to the transmission control valve and supplies thetorque converter with the remainder of the oil.

The transmission control valve controls three directional clutches andthree speed clutches. The differential valve, check valve and dump valveare part of the transmission control valve.

The torque converter inlet relief valve is located in the transmission casebelow the control valve.

¥ Transmission controlvalve controls:

- Three speedclutches

- Three directionalclutches

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The oil-to-water cooler is located in the bottom tank of the radiator.

NOTE: The colors in the sectional views and hydraulic schematicsthroughout this presentation denote various pressures within thesystem. The legend of color codes is as follows:

Red - Pump supply and P1 pressure

Red and White Stripes - Reduced and P2 pressure

Red Dots - Second reduction of supply pressure

Pink - Third reduction of supply pressure

Orange - Signal, pilot or torque converter oil

Green - Open to tank

Blue - Blocked oil

Yellow - Activated valve envelopes ormoving parts

Brown - Lube oil

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25

1. Transmission filltube

2. Transmission oilfilter

3. Transmission sightgauge

4. Side cover

The transmission fill tube (1) is on the left side of the machine near thearticulation joint. The fill tube contains a dipstick.

The transmission oil filter (2) is on the inside of the frame on the left sideof the machine. The filter housing contains a pressure tap to checktransmission supply pressure and an S¥O¥S tap for taking transmission oilsamples.

The transmission sight gauge (3) and the transmission filter are accessedthrough the opening behind the steps on the left side of the machine.

The transmission sight gauge is on the left side of the machine behind thesteps. Maintain the transmission oil level between the LOW mark and theHIGH mark on the sight gauge when the transmission is warm and to thetop of the sight gauge when the transmission is cool.

Access to the transmission control valve and pressure taps can be obtainedby removing the side cover (4) on the right side of machine.

1

3

2

4

¥ Identify components:

1. Dump valve

¥ Identify pressure taplocations:

2. Torque converteroutlet

3. P1

4. P2

5. P3

26

2

4

5

3

1

Shown in this view is the transmission control valve mounted on thetransmission. A dump valve (1) is mounted to the control valve.

Three pressure taps are provided on the transmission control valve forchecking P1 speed clutch pressure (2), P2 directional clutch pressure (4)and P3 torque converter inlet pressure (5).

Use pressure tap (2) to check torque converter outlet pressure.

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27

¥ Valve components

3

321

2

1

46

4

6

5

5

DIFFERENTIAL VALVE

FWDHIGH

FWD HI FWD LO REV

1ST SPD 2ND SPD 3RD SPD

2NDSPEED

3RDSPEED

1STSPEED

SELECTORSPOOL

DUMPSPOOL

ORIFICE

PISTON

SLUG

MODULATINGRELIEF VALVE

BACK FLOWCHECK VALVE

PUMPSUPPLY

LOADPISTON

ORIFICECHECKVALVE

TRANSMISSION CONTROL VALVENEUTRAL

FWDLOWREV

The 4F/3R transmission control valve has six solenoids which controlthree directional clutches and three speed clutches. The transmissioncontrol valve also contains the following components: speed anddirectional spools, dump valve, backflow check valve, differential valve,modulating relief valve and load piston, and orifice check valve.

Loss of electrical power to any speed or directional solenoid will preventthat particular clutch from engaging.

The transmission control valve for the 924G/924Gz is very similar to thetransmission control valve that was used on the 924F/IT24F.

INSTRUCTOR NOTE: For more detailed information about theoperation of the transmission control valve, Technical InstructionModule "Electronically Controlled Power Shift Transmission ControlValve" (Form SEGV2572).

- Loss of electricalpower preventsshifting

STMG 717 - 35 -11/99

28

¥ Electronic transmissioncontrol systemcomponents

SOLENOID

SOLENOID

SOLENOID

SOLENOID

SOLENOID

SOLENOID

DIAGNOSTICINDICATOR

TRANSMISSION NEUTRALIZEROVERRIDE SWITCH

SHIFTLEVER

TRANSMISSIONNEUTRALIZER SWITCH

SERVICECONNECTOR

AUTO/MANUALSWITCH

HARNESS CODECONNECTOR

ENGINE SPEEDSENSOR

TRANSMISSIONSPEED SENSOR

TRANSMISSION

ELECTRONIC TRANSMISSION CONTROL SYSTEM

RIDE CONTROL/LOADCHECK SWITCH

PARK BRAKESWITCH

DOWNSHIFTSWITCH

F-N-R SWITCH

SPEEDOMETER

ELECTRONICCONTROLMODULE

PARK BRAKEALARM RELAY

RIDE CONTROLLOAD CHECK RELAY

Electronic Transmission Control System

This graphic shows a block diagram for the electronic transmissioncontrol system. The electronic control module (ECM) receives inputsfrom the operational controls, harness code, and sensors. Based on theinputs that it receives, the ECM shifts the machine, activates relays orsends signals to the diagnostic indicator .

The electronic transmission control system inputs consist of the followingcomponents:

STMG 717 - 36 -11/99

Shift lever - allows the operator to choosetransmission speed and direction

Downshift switch - allows the operator to manuallydownshift the transmission

Neutralizer switch - neutralizes the transmission when theoperator ENGAGES the servicebrakes

The electronic control system outputs consist of the followingcomponents:

INSTRUCTOR NOTE: This electronic control system is similar tothat on the 928G/IT28G. For more information, refer to STMG 694"928G Wheel Loader/IT28G Integrated Toolcarrier" (FormSESV1694).

STMG 717 - 37 -11/99

Neutralizer override switch - overrides the transmission neutralizerswitch

Auto/Manual switch - ON/OFF switch for the electronictransmission control system

Transmission speed sensor - indicates transmission speed

Engine speed sensor - indicates engine speed

Transmission solenoids - control transmission speed anddirection

Ride control/load checkswitch

- OFF/ON/AUTO switch for ridecontrol

Park brake switch - neutralizes the transmission when theparking brake is ENGAGED

F-N-R switch - allows the operator to change thetransmission direction

Diagnostic indicator - flashes fault codes

Park brake alarm relay - alerts the operator if the park brake ison during operation

Ride control/load check relay - activates/deactivates the ride controlsystem

Speedometer - indicates machine speed to theoperator

STMG 717 - 38 -11/99

29

¥ Operational inputsand ECM

1. Transmissioncontrol lever

2. Transmissioncontrol (F-N-R)switch

3. Downshift button

4. Pressure switches

5. Electronic controlmodule (ECM)

Shown in these views are the main operational input mechanisms and theECM.

The transmission control lever (1) is identical to the lever that is used inthe 928G/IT28G.

A transmission control (F-N-R) switch (2) is an option. This switch isintegrated into the joystick control lever if the machine is equipped withthis option. The downshift button (3) is on the front of the joystickcontrol lever.

The transmission neutralizer on the 924G/924Gz uses two pressureswitches (4) located on the brake valve instead of one mechanical switchwhich was used on the 924F/IT24F. Using two pressure switchesprovides smoother neutralization of the transmission when the brakes areapplied and smoother engagement of the transmission when the brakes arereleased.

The ECM (5) is located under the cab on the right side.

1

4

3

2

5

¥ Axle contains inboardplanetary final drives

30

Axles

The axles contain inboard planetary final drives. The front axle is fixed tothe frame, but the pinned rear axle allows 15¡ oscillation in each directionwith 15.5 or 17.5-25 tires.

The axles are an oversize casting to allow for future brake improvements.A new mounting of the front axle to the front frame gives a more rigidstructure to the machine. An integrated lip was added to the casting toprotect the Duo Cone seals in waste handling applications.

STMG 717 - 39 -11/99

31

¥ Axle similar to otherwheel loaders

FRONT / REAR AXLE

INBOARDPLANETARY

BEVEL GEARAND PINION

DIFFERENTIAL

SUN GEARSHAFT

AXLE

The axle is similar to the axles on other Caterpillar Wheel Loaders. Thestandard axle contains a conventional differential and fully enclosed wetdisc brakes with a single disc for each wheel. The axle can be orderedwith a limited slip differential. A NoSPIN differential is available forspecial orders.

The transmission output shaft transmits power to the bevel pinion shaftand bevel gear and pinion assembly in the front and rear axles. The bevelgear and pinion assembly transfers power to the differential. Thedifferential transmits power to the sun gear shafts. The sun gear shaftstransmit power to the inboard planetaries. The motion of the planetcarriers causes the axle shafts to rotate.

- Optional limited slipdifferential

- NoSPIN differentialavailable

¥ Power flow:

- Drive shaft - Bevel pinion shaft - Differential - Sun gear shaft - Planet gears - Planet carriers - Axle shaft

STMG 717 - 40 -11/99

¥ Parking Brake

32

The transmission is neutralized when the parking brake is applied. Thisneutralizer is a mechanical switch and can be overridden. The parkingbrake transmission neutralizer switch is the same as that used on the928G/IT28G.

STMG 717 - 41 -11/99

¥ Three hydraulicsystems

- Steering system

- Brake/fan drive

- Work tool hydraulicsystem

33

HYDRAULIC SYSTEMS

There are three major hydraulic systems on the 924G/924Gz: the steeringsystem, the brake system/fan drive system, and the work tool hydraulicsystem. All three systems share a common hydraulic tank.

The steering system and the brake/fan drive hydraulic system on the924G/924Gz are very similar to those on the 928G/IT28G. The work toolhydraulic system, however, is different.

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34

¥ Vented hydraulic tank

1. Clean-out hole

2. Sight glass

3. Hydraulic oil filter

4. Ecology drain

All three hydraulic systems share a common tank which is located behindthe cab. The tank has changed from a pressurized tank to a vented tank.Also, a large clean-out hole (1) in the tank allows for easier flushing andcleaning for service.

The sight glass (2) on the hydraulic tank has been moved to the left side ofthe tank on the outside of the machine. This makes the sight glass easierto check during maintenance.

The hydraulic oil filter (3) on the 924G/924Gz is plumbed into the fandrive system and is located in front of the cooling package. The S¥O¥Sport is part of the filter base. This filtration system is similar to the928G/IT28G.

The ecology drain (4) function is now provided by a manual shut-offvalve. This valve is located on the left side of the machine at the front ofthe engine access door.

1

3

2

4

¥ Work tool hydraulicsystem

- Closed center valvesin parallel

- Variable flow axialpiston pump

35

Work Tool Hydraulic System

The pilot operated work tool hydraulic system on the 924G/924Gz is verydifferent from the previous hydraulic system. The 924F/IT24F machinesuse an interrupted series flow hydraulic system with open center, pilotoperated control valves and a fixed displacement pump. The924G/924Gz machines use a parallel flow hydraulic system with closedcenter, pilot operated control valves and a load sensing, variable flowaxial piston pump. The improvements have been made to the hydraulicsystem in order to increase the versatility of the 924G.

The tilt circuit of the 924G is different from the tilt circuit of the 924Gz.With the Versa Link© linkage on the 924G, extending the cylinder will tiltthe work tool forward and retracting the cylinder will rack the work toolback.

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¥ 924G tilt circuit

¥ 924Gz tilt circuit

36

On the 924Gz, the tilt cylinder must extend in order to tilt the bucket backand retract to dump the bucket.

The 924Gz and the 924G both benefit from the improved hydraulicsystem. The load sensing system only consumes horsepower from theengine when needed. The load check poppets in each bank valve allowalmost zero drift and there is almost zero voiding in the cylinders.

STMG 717 - 45 -11/99

STMG 717 - 46 -11/99

37

¥ Work tool hydraulicsystem for 924G

The work tool hydraulic system on the 924G and the 924Gz consist of thefollowing components:

WORK TOOLPUMP

STEERINGPUMP

FROMBRAKE/FAN

DRIVE SYSTEM

TO SECONDARYSTEERINGPRESSURE

SWITCH

MANIFOLD

SIGNAL FROMSTEERINGSYSTEM

COUPLERCONTROL

VALVE

PRESSUREREDUCING

VALVE

BACKPRESS.VALVE

SINKVALVE

PILOT CONTROL VALVES

TO AUXILIARYFUNCTION

TO AUXILIARYFUNCTION

OPTIONAL RIDECONTROL SYSTEM

LIFTCYLINDERSCOMBINATION VALVE

TILTCYLINDER

924G WORK TOOLHYDRAULIC SYSTEM

TO STEERINGSYSTEM

FROMBRAKE

PISTONS

AUXILIARYCONTROL

VALVE

AUXILIARYCONTROL

VALVE

LIFTCONTROL

VALVE

TILTCONTROL

VALVE

Work tool pump - Provides flow to the bank valves

Steering pump

Pressure reducing valve

- Provides flow to the pressure reducingvalve and the steering system

- Limits the maximum pressure of thepilot oil

Pilot control valves - Control the flow of pilot oil to the bankvalves

- Control the flow of supply oil to thecylinders or the work tools

Bank valves

Ride control system - Functions as a shock absorber bycushioning the ride at high speeds

Sink valve - Drains the oil from the signal networkwhen none of the bank valves areactivated

The following components are on the 924G only:

STMG 717 - 47 -11/99

Coupler control valve

Coupler engagement cylinders

Back pressure valve

- Controls the flow of oil to the couplerengagement cylinders

- Move the engagement pins on the worktool coupler

- Maintains a small amount of pressurein the return galley of the valve bank inorder to assist in the opening of themakeup valves

Combination valve - Performs the relief function on thehead end of the tilt cylinder

STMG 717 - 48 -11/99

38

¥ Work tool hydraulicsystem for 924Gz

This view shows a block diagram of the 924Gz work tool hydraulicsystem. The machine is not equipped with a coupler control valve,coupler engagement cylinders or a combination valve.

Since the 924Gz tilt circuit is configured differently, the combinationvalve is not necessary.

WORK TOOLPUMP

STEERINGPUMP

FROMBRAKE/

FAN DRIVESYSTEM

TO SECONDARYSTEERINGPRESSURE

SWITCH

MANIFOLD

FROMSTEERINGSYSTEM PRESSURE

REDUCINGVALVE

BACKPRESS.VALVE

SINKVALVE

PILOT CONTROL VALVES

TO AUXILIARYFUNCTION

TO AUXILIARYFUNCTION

OPTIONAL RIDECONTROL SYSTEM

LIFTCYLINDERSTILT CYLINDER

924Gz WORK TOOLHYDRAULIC SYSTEM

TO STEERINGSYSTEM

TILTCONTROL

VALVE

LIFTCONTROL

VALVE

AUXILIARYCONTROL

VALVE

AUXILIARYCONTROL

VALVE

FROM BRAKEPISTONS

¥ Hydraulic pumps

1. Steering pump

2. Work tool pump

3. Signal pressure tapfor steering pump

4. Signal pressure tapfor work tool pump

39

The work tool hydraulic pump (2) has changed from a vane pump to avariable displacement axial piston pump. The steering (1) and work toolpumps are located under the left side of the cab, which is in the same areaas the pumps on the 924F/IT24F. The steering pump is mounted onto thework tool pump.

The signal pressure taps (3) and (4) are located on the compensator valvesfor the steering and work tool pumps.

There are separate suction lines for the work tool and steering pumps.

STMG 717 - 49 -11/99

1

3

24

- Separate suctionlines

STMG 717 - 50 -11/99

40

¥ Load sensing worktool hydraulic systemand steering systemuse variabledisplacement pumps

This view shows a cross sectional view of the work tool pump or thesteering pump. These pumps are variable displacement axial pistonpumps and are similar to the variable displacement pumps on otherCaterpillar machines.

The pump has one swashplate actuator piston which adjusts the angle ofthe swashplate.

The compensator valve controls the flow of oil to the swashplate controlpiston and thereby controls the pump output. Inside the compensatorvalve are the margin spool and the cutoff spool.

The margin spring maintains the pump supply pressure higher than thesignal pressure. The cutoff spring controls the maximum system pressure.

The work tool pump provides flow for only the bank valves. The steeringpump provides flow for the pilot system and the steering system.

MARGINSPRING

MARGIN SPOOL

ACTUATOR PISTON

BIAS SPRING

SWASHPLATE

SIGNAL

PUMP OUTPUT

CONSTANT FLOWPUMP OPERATION

CUTOFFSPRING

CUTOFF SPOOL

- Steering pumpprovides pilot oilflow

NOTE: Depending on the adjustments made to the margin spool andthe amount of pump leakage, LOW PRESSURE STANDBY andmargin pressure can be equal. However, margin pressure can neverbe higher than LOW PRESSURE STANDBY.

INSTRUCTOR NOTE: This pump is similar to the implementhydraulic pump on the Challenger 35/45/55 Agricultural Tractors.For information on the operation of this pump, see STMG 667-01"Challenger 35/45/55 Agricultural Tractors--Implement, Hitch andSteering Systems" (Form SESV1667-01).

STMG 717 - 51 -11/99

1. Pressure reducingvalve

2. Combination valve

3. Pilot oil pressuretap

4. Steering systempressure tap

5. Tilt head endpressure tap

6. Tilt rod endpressure tap

41

The pressure reducing valve is located on the right side of the machineunder the cab. Oil flows from the steering pump to the pressure reducingvalve (1). The reduced pressure oil is the pilot oil.

The pressure reducing valve limits the maximum pressure in the pilotsystem. This is the same pressure reducing valve as that used in the924F/IT24F.

The pilot oil pressure tap (3) and the steering system pressure tap (4) arelocated on the pressure reducing valve.

The combination valve (2) is located next to the pressure reducing valve.The combination valve is only on the 924G and consists of both a divertervalve and a relief valve. This valve performs the relief function for thehead end of the tilt cylinder on the 924G.

The tilt head end pressure tap (5) and the tilt rod end pressure tap (6) arelocated on the combination valve.

STMG 717 - 52 -11/99

1

2

3

4

5

6

¥ Pilot Control Valves

42

From the pressure reducing valve, pilot oil flows through a screen to thepilot control valves. This screen was not used on the 924F/IT24F.

The pilot control valves are located in the right side console inside thecab.

The pilot control valves have been designed to allow for less lever effort.They operate in the same manner as the pilot control valves on the924F/IT24F. The pilot control valves control the flow of pilot oil to thebank valves.

NOTE: There is no longer a mechanical lock on the pilot valve forthe third function of the hydraulic system. The lock was used toprevent accidental uncoupling of the work tool. But, since this leverdoes not control the work tool coupler, the lock on this lever is notnecessary. The work tool coupler is controlled by a switch on theright console.

STMG 717 - 53 -11/99

- Location

- Operation

STMG 717 - 54 -11/99

43

¥ Bank valves From the work tool pump, the oil flows to the closed center, pilot operatedbank valves. Shown here is an individual bank valve.

The bank valves control the flow of hydraulic oil from the implementpump to the cylinders. The valves also send signal oil back to the worktool pump.

Each bank valve operates differently, but all of the valves share the samebasic components.

A common galley carries pressure oil from the work tool pump to all thebank valves. Also, a common galley carries return oil away from the bankvalves to the tank.

Resolvers determine which function in all of the valves has the highestdemand. Then, the signal for the highest demand is sent to the pump.The resolvers are double check valves containing two balls.

RETURN GALLEY

SIGNAL NETWORK

SUPPLY GALLEY

DRAIN PASSAGE

COMBINATION VALVE TILT CONTROLCALVE

AREA CONTROLSPOOL

AREA CONTROLSPOOL

POPPET POPPET

RESOLVER

RELIEFVALVE

MAKEUPVALVE

CHECK VALVE

MAIN CONTROLSPOOL

SINKVALVE

924G TILT CONTROL VALVETILT BACK

INLETMANIFOLD

TO TANK

SIGNAL TOCOMPENSATOR VALVE

FROMPUMP

FROM PILOTCONTROL VALVE

TO PILOTCONTROL VALVE

TO TANK

- Control flow to thecylinders

¥ Common components

- Pressure galley

- Return galley

- Resolvers

Each valve has two poppets which act as a lock valve. The poppets closeoff the ports so that there is almost zero drift of the work tools when thebank valve is in the HOLD position. Passages in the poppet allow arestricted amount of oil to flow from the port in the valve to the back sideof the poppet.

Every poppet is controlled by an area control spool that is located directlybehind the poppet. Pilot oil opens these spools by forcing the spoolupward. Moving the spool upward opens the back side of the poppet tothe tank. The poppet is opened by the area control spool in order to allowreturn oil to flow from the port to the main control spool.

The main control spool is controlled by pilot oil from the pilot controlvalves. The spool is machined differently for each bank valve.

STMG 717 - 55 -11/99

- Main control spool

- Area control spools

- Poppets

STMG 717 - 56 -11/99

44

¥ Bank valvecomponents

This view shows the components of the tilt control valve for the 924G.

POPPETRESOLVER

MAIN CONTROLSPOOL

PRESSUREGALLEY

RETURNGALLEY

AREACONTROL

SPOOL

STMG 717 - 57 -11/99

45

During the dump cycle, the tilt control valve on the 924G regeneratesreturn oil from the rod end of the cylinder and sends it to the head end ofthe cylinder. This regenerated oil flows through the pressure galley and isequal to pump output pressure. The result is that the pressure on bothsides of the piston is equal to the pressure in the pressure galley.

Pressure equalization prevents the head end of the tilt cylinder fromvoiding, resulting in a powered dump rather than the bucket dumping dueto the force of gravity. During simultaneous lift and dump operations, thisaction also provides additional supply oil so both the tilt and lift circuitsoperate smoothly. Without pressure equalization, the pump would not beable to mee the flow needs of both circuits, resulting in the lift function tobe slower than desired.

The tilt control valve for the 924G is the only valve that regenerates oiland equalizes pressure.

MAIN CONTROLSPOOL

RESOLVER

AREA CONTROLSPOOL

ORIFICE

RETURNGALLEY

ROD ENDPORT

HEAD ENDPORT

POPPET

924G TILT CONTROL VALVEDUMP

SUPPLYGALLEY

¥ Tilt control valve for924G

- Regeneration ofreturn oil

- Pressureequalization incylinder withpressure galley

¥ Dump Operation

- Spool

To begin the dump cycle, pilot oil flows into the right end of the spool.The spool starts to shift to the left, connecting the pressure oil passage tothe left poppet and the right poppet.

Pilot oil also flows through an orifice to the bottom side of the right areacontrol spool and the area control spool shifts upward. The oil from theback side of the right poppet begins to flow to the return passage in thevalve to be regenerated.

At the same time, supply oil flows past the spool and encounters theresolver which is next to the poppet. If the pressure oil in the valve is at ahigher pressure than the pressure in the signal passage, the ball unseatsand the oil signals the pump to upstroke to meet the flow demand. If thepressure oil in the valve is at a lower pressure than the signal passage, thepump will already be upstroked by another circuit, but the pump willupstroke more to meet the additional flow demand of the tilt circuit.

The left poppet is opened by the supply oil and oil flows out to the headend of the cylinder.

As supply oil flows out to the cylinder, the pressure of the return oilincreases. Return oil flowing through the right poppet causes a pressuredrop across the poppet and it opens.

Now, system pressure is open to both the rod end and the head end of thetilt cylinder. The bucket dumps because of two factors: the effective areaof the head side of the piston is greater than the effective area of the rodside of the piston and the weight of the load and the bucket. These twoforces cause the cylinder to extend and the bucket dumps.

Pressure oil flows out to the head end of the cylinder. Return oil flowsback from the rod end of the cylinder and is sent through the pressure oilpassage to the head end of the cylinder. Oil from the back side of theright poppet also flows into the passage that is between the right poppetand the spool. In this manner, nearly all of the return oil is regenerated.

STMG 717 - 58 -11/99

- Regeneration of oil

- Pressureequalization

- Right poppet

- Left poppet

- Resolver

- Area control spool

STMG 717 - 59 -11/99

46

¥ Tilt back operation During tilt back, the valve does not regenerate return oil, nor are thepressures equalized on each side of the piston in the cylinder.

Pilot oil flows into the left end of the spool. The spool starts to shift to theright. This connects the pressure oil passage to the right poppet and thereturn passage to the left poppet.

Pilot oil also flows through the orifice to the bottom side of the left areacontrol spool and the area control spool shifts upward. The oil from theback side of the left poppet to begins to return to tank.

The pressure oil flows past the spool and encounters the resolver which isnext to the poppet. The resolver senses the oil pressure and sends theappropriate signal to the pump. The pump upstrokes because of theincrease in the flow demand.

MAIN CONTROLSPOOL

RESOLVERAREA CONTROL

SPOOL

ORIFICE

RETURNGALLEY

ROD ENDPORT

HEAD ENDPORT

POPPET

924G TILT CONTROL VALVETILT BACK

SUPPLYGALLEY

- Resolver

- Spool

- Area control spool

- Right poppet The right poppet is opened by the supply oil and oil flows out to the rodend of the cylinder.

As supply oil flows out to the cylinder, the pressure of the return oilincreases. Return oil flowing through the left poppet causes a pressuredrop across the poppet and it opens. Return oil flows from the head endof the cylinder to tank.

Supply oil continues to flow past the right poppet and out to the cylinder.Return oil flows past the left poppet. The cylinder retracts and the buckettilts back.

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- Left poppet

STMG 717 - 61 -11/99

47

¥ Pressure relief andmakeup valves

The tilt control valve on the 924G also includes a pressure relief valve anda makeup valve.

The direct acting pressure relief valve is connected to the rod end of thetilt control cylinder. It is in parallel to the shoulder of the rod end poppetin the valve.

The makeup valve is connected to the head end of the tilt control cylinder.This valve is in parallel to the shoulder of the head end poppet in thevalve. The makeup valveÕs purpose is to provide oil to the head end of thecylinder during dumping operations when extra supply oil is needed.

MAKEUP VALVE RELIEF VALVE

- Makeup

- Pressure relief

STMG 717 - 62 -11/99

48

¥ Combination valve Plumbed into the tilt control cylinder on the 924G is a combination valvewith a diverter valve and a relief valve. The combination valve performsthe relief function on the head end of the cylinder during backdragging.

This slide shows the combination valve during a back drag operation. Thebucket is forcing the cylinder piston in, thus causing a void on the rod endand pressure on the head end of the cylinder.

The spool in the diverter valve is connected to each end of the tiltcylinder. The function of the diverter is to sense the pressure differentialbetween the head end and the rod end of the cylinder. If the pressuredifferential exceeds 3000 KPa (435 psi), the diverter opens and oil fromthe head end of the cylinder flows to the relief valve. If the pressure onthe relief valve exceeds 12,300 KPa (1780 psi), the relief valve opens andthe oil is returned to tank.

The reason for the diverter valve is to keep the relief valve setting low andyet allow for the high pressures needed for the pressure equalization of thetilt circuit during the dump operation.

COMBINATION DIVERTER/RELIEF VALVEBACK DRAG OPERATION

TILTCYLINDER

¥ Ride control system

49

Shown here is the ride control valve. This valve is located at the bottomof the frame on the left side of the machine.

The optional ride control system on the 924G/924Gz is very similar to theride control system on the 924F/IT24F. However, the new auto ridecontrol system is factory set to activate at 8 km/h (5 mph).

The auto ride activation speed is now programmable. The ElectronicTechnician (ET) service tool can be used to select an activation speedbetween 5 and 15 km/h (3 and 9 mph). This customizes the ride controlactivation to the job site and allows the operator to concentrate more onoperating the machine rather than turning ON or OFF the ride controlsystem.

STMG 717 - 63 -11/99

¥ Ride controlaccumulator

50

The ride control system uses one accumulator (arrow). This accumulatoris located on the left side of the machine.

A floating piston in the ride control accumulator separates the oil from thenitrogen gas. Since nitrogen gas is compressible, the gas serves as aspring. Any downforce on the lift arms is transferred through the oil atthe head end of the lift cylinders to the accumulator. The force in the oilis transmitted to the accumulator piston, which compresses the nitrogengas. Compressing the nitrogen gas absorbs the pressure spike and the oildisplacement caused by the downward force on the lift arms. Thisoperation results in less ground induced shocks on structures andcomponents, reduced tire flexing and a greater payload retention.

STMG 717 - 64 -11/99

STMG 717 - 65 -11/99

51

¥ Steering systemcomponents

- Steering pump

- Steering meteringpump

- Steering cylinders

- Secondary steeringsystem

Steering System

The hydraulic steering system steers the machine by changing themachineÕs angle of the articulation.

The steering system consists of the following components: steeringpump, steering metering pump and steering cylinders. A secondarysteering system is an option on this machine.

The basic operation of the steering system has not changed from the924F/IT24F. However, some modifications to the components of thesystem have improved the steering performance of the 924G/924Gz.

INSTRUCTOR NOTE: The steering system is similar to that on the928G/IT28G. For more information, refer to STMG 694 "928GWheel Loader/IT28G Integrated Toolcarrier" (Form SESV1694).

METERINGSECTION

CONTROLVALVE

SECTION

CROSSOVERLINE RELIEF

VALVESSUPP.

STEERINGPUMP

IMPLEMENTPUMP

STEERINGMETERING PUMP

LEFTSTEERINGCYLINDER

RIGHTSTEERINGCYLINDER

LOAD SENSING STEERING SYSTEM

M

RELIEFVALVE

STEERINGPUMP

TO IMPLEMENT VALVES

TO PILOT SYSTEM

FROMBRAKES

RIGHT TURN

¥ Steering pump

1. Variabledisplacement axialpiston pump

2. Signal pressure tap

52

The steering pump (1) provides flow to the steering cylinders. Thesteering pump is a variable displacement axial piston pump. The steeringmetering pump sends a signal to the pump and the pump upstrokes ordestrokes to meet the flow demand.

The steering pump is located on the left side of the machine under the caband is driven by the implement pump.

Signal pressure tap (2) is located on the compensator valve. The steeringpump output pressure tap is located on the pressure reducing valve.

This is the same style of variable displacement piston-type pump as thework tool hydraulic pump.

STMG 717 - 66 -11/99

1

2

¥ Steering meteringpump components:

- Control valvesection

- Metering section

- Crossover line reliefand makeup valves

- Check valves

53

The steering metering pump (arrow) controls the flow of oil from thesteering pump to the steering cylinders. The steering metering pump islocated under the front of the cab.

The steering metering pump consists of a control valve section, ametering section, crossover line relief and makeup valves, and a checkvalve. A mechanical linkage connects the steering wheel to the controlvalve and metering sections of the steering metering pump.

The new steering metering pump allows for a wider range of modulation.This provides smoother steering and better control of the machine.

STMG 717 - 67 -11/99

¥ Steering cylinders

54

The steering cylinders change the machineÕs angle of articulation.

A steering cylinder is located on each side of the articulation joint of themachine.

The pins and bores on the steering cylinders have been made longer onthe 924G/924Gz than on the 924F/IT24F. Also, the bosses for thesteering cylinders are thicker. These changes will decrease the contactstresses in the cylinders and increase the pin bore life.

STMG 717 - 68 -11/99

- Located on eachside of the machine

- Pins and boreslonger

¥ Supplemental steeringsystem

1. Hydraulic pump

2. Electric motor

55

A secondary steering system is an option on the 924G/924Gz whichallows the operator to continue to steer the machine if the engine fails orthe steering pump stops. The system consists of a hydraulic pump (1) thatis driven by an electric motor (2), which are located below the coolingpackage in front of the fuel tank. The ECM controls the motor through arelay.

If the steering pressure drops, a signal from the control module closes acontact and the secondary steering pump starts. The secondary steeringmotor, relay and pump are located at the rear of the machine in front ofthe fuel tank.

The secondary steering system is retrofittable onto a 924G/924Gz.

The secondary steering system has a manual test and an auto test toensure correct operation. The auto test consists of a three second testwhen the start key is in the ON position, prior to turning over the engine.During the test, the operator should steer the machine and confirm that thesystem works properly.

STMG 717 - 69 -11/99

12

- Operation

- Retrofittable

- Manual test and autotest

STMG 717 - 70 -11/99

56

¥ Brake hydraulicsystem

- Identify components

Brake/Fan Drive System

The brake hydraulic system maintains the hydraulic pressure necessary toapply the service brakes. The major components of this system are: thepump, the brake accumulator charging valve group, the accumulators, thebrake control valve and the brake pistons (located in the axle).

This hydraulic system also powers the cooling fan. Therefore, it will bereferred to as the brake/fan drive system.

The brake/fan drive system is a new design feature on the 924G/924Gz.However, this system is similar to the brake/fan drive system that is usedon the 928G/IT28G.

INSTRUCTOR NOTE: The brake/fan drive system is similar to thaton the 928G/IT28G. For more information, refer to STMG 694"928G Wheel Loader/IT28G Integrated Toolcarrier" (FormSESV1694).

FRONTBRAKE

ACCUMULATOR

REARBRAKE

ACCUMULATOR

TANDEMBRAKEVALVE

REAR AXLEBRAKES

FRONT AXLEBRAKES

PRIORITYVALVE

MOTOR GROUP

ENGINE FAN

FILTER

RELIEFVALVE

SHUTTLEVALVE

CHECKVALVE

BRAKE ANDFAN PUMP

COOLER

BRAKE SYSTEMCUT-IN/BRAKES RELEASED

CUT IN/CUT OUTVALVE

ACCUMULATOR CHARGINGVALVE

- Drives cooling fan

¥ Brake/fan drive pump

1. Gear pump

2. Brake accumulatorcharging valvegroup

3. Brake accumulatorpressure tap

4. Pressure switch

57

The brake hydraulic pump (1) has changed from a vane pump on the924F/IT24F to a gear pump on the 924G/924Gz. This is the same pumpthat powers the cooling fan. The pump has also changed location. It is nolonger mounted onto the other pumps, but is now located on the right sideat the rear of the engine.

The accumulator charging valve (2) is attached to the brake/fan drivepump. This valve group directs the oil flow from the pump to either theaccumulators or the fan drive system depending on the pressure in theaccumulators.

The accumulator charging valve creates priority for charging the brakeaccumulators over the cooling fan drive. The operation of theaccumulator charging valve is different from that on the 924F/IT24F, butit is similar to that used on the 928G/IT28G.

The pressure switch (4) activates the brake pressure warning lamp andalarm on the left front console when pressure in the brake system is low.

Use the pressure tap (3) to check the CUT-IN and CUT-OUT pressures.There are no adjustments for CUT-IN and CUT-OUT pressures, so if thepressures are not correct, replace the accumulator charging valve.

STMG 717 - 71 -11/99

1

2 3

4

¥ Brake accumulators

58

The brake accumulators (arrow) have changed location from the924F/IT24F and are now mounted vertically onto the right side of thehydraulic tank support. The precharge pressure in the accumulators hasbeen reduced.

The accumulators store fluid energy for quick response of the brakes.

STMG 717 - 72 -11/99

¥ Brake control valve

59

The brake control valve is located under the front of the cab. The valve ismanually actuated by foot. The brake control valve directs oil from theaccumulators to the brake pistons.

Pressing the brake pedal directs oil from the system to the brake pistonsand releasing the brake pedal allows oil from the brake pistons to return totank.

The maximum pressure has been reduced in order to accommodate for thechange to the seals on the brake pistons.

The valve linkage has also changed from the 924F/IT24F to accommodatethe use of the suspended brake pedal. However, the operation of thebrake control valve has not changed.

STMG 717 - 73 -11/99

- Maximum pressuredecreased

STMG 717 - 74 -11/99

60

¥ Disc brakes Each brake disc rotates with the sun gear shaft. The brakes arehydraulically engaged. When the brake pressure is drained, the pistonseals and retraction springs retract the piston to RELEASE the brakes.

The seals on the brake pistons are a D-ring design which are easier toservice and install than the seals used on the 924F/IT24F. Because of thelower pressure in the brake system, the piston size has increased. Theincrease in effective area allows the pistons to apply the same brake forcewith lower pressure. The brake piston and the reaction plate are heavier,providing better dissipation of heat.

The discs have increased in surface area in order to improve service lifeand performance. There is now one disc per wheel and the disc isdesigned with a cross-hatch pattern for better oil flow.

REACTIONPLATE

BRAKEPISTON

BRAKEDISC

SUN GEAR SHAFT

DISCBRAKES

- Brake discs

- Brake pistons

61

CONCLUSION

This concludes the introduction presentation on the 924G and the 924GzWheel Loaders.

This presentation discussed the component locations and systemsoperation of the power train and hydraulics systems on these wheelloaders. When used in conjunction with the service manual, theinformation in this package should permit the serviceman to do athorough job of troubleshooting these systems and diagnosing problemson the machines.

STMG 717 - 75 -11/99

1. 924G machine cutaway2. 924F model view3. 924G configuration4. 924Gz configuration5. Hood and cab6. Front of cab7. Door latch release8. Seat9. Left front console

10. Center front console11. Right front console12. Work tool control levers13. Right console14. Pedals15. Fuse box16. Engine and fuel tank17. Cooling system18. Starting and charging system19. Electrical components -- Left side20. Electrical components -- Right side21. 924G powertrain cutaway22. Torque converter23. Transmission cutaway24. Powertrain hydraulic system25. Transmission service points26. Transmission control valve27. Transmission control valve schematic28. Electronic transmission control system

block diagram29. Transmission controls30. Front axle31. Axle cutaway32. Parking brake33. 924G hydraulic cutaway34. Hydraulic tank35. 924G hydraulic cutaway36. 924Gz hydraulic cutaway37. 924G work tool hydraulics block diagram38. 924Gz work tool hydraulics block diagram39. Hydraulic pumps

40. Hydraulic pump cutaway41. Pressure reducing valve and combination

valve42. Pilot control valves43. Schematic of 924G tilt control valve44. Bank valve components45. 924G tilt control valve dump operation46. 924G tilt control valve tilt back operation47. 924G tilt control valve makeup valve and

relief valve48. Combination valve schematic49. Ride control valve50. Ride control accumulator51. Steering system schematic52. Steering pump53. Hand metering unit54. Steering cylinder55. Secondary steering pump56. Brake system schematic57. Brake pump58. Brake accumulators59. Brake control valve60. Brakes cutaway61. 924G machine cutaway

SLIDE LIST

STMG 717 - 76 -11/99

COOLANTSWITCH

T°

399-OR

RESISTOR

396-PK-18

377-OR

310-PU

RESISTOR FROMLAMP

SWITCH

373-GN

102-RD

10 A115-RD

112-PU

G S

MTR BAT

FIRST GEARSECOND GEARTHIRD GEARFOURTH GEARSTART RELAYNEUTRALREVERSEFORWARD

+ BATTERYGROUNDEXTERNAL FWDEXTERNAL REVBACKUP REALYKEY SWITCH IN

RD-00

105-RD

307-OR

304-WH

109-RD

306-GN

B-

B+

D+

109-RD

308-YL

117-RD

R

C

S

B ST

OFF

ON

101-RD

30

60

60

109-RD

109-RD

115-RD

LAMP BREAKER

15

R

924G STARTING AND CHARGING SYSTEM

POSNEGPOSNEG

15 A

MOTOR

TO SERVICE METER ANDSECONDARY STEERING CONTROL

188-WH

AB

C

D

E

F

G

H

I

J

K

L

N

M

STM

G 717

- 77-

Serviceman's H

andout No. 1

11/99Startintg and Charging SystemComponents

Directions: Fill in the blank next to theletters with the correct component name.

A.

B.

C.

D.

E.

F.

G.

H.

I.

J.

K.

L.

M.

N.

STMG 717 - 78 - Serviceman's Handout No. 211/99

Work Tool Hydraulic Component Checklist

Directions: Use this sheet to take notes during the slide presentation. During a lab exercies, use thissheet as a checklist when identifying and locating components.

Work Tool Pump

Steering Pump

Pressure Reducing Valve

Pilot Control Valves

Sink Valve

Tilt Control Valve

Lift Control Valve

Auxiliary Control Valve

Back Pressure Valve

Tilt Cylinder

Lift Cylinders

Coupler Control Valve (924G only)

Coupler Engagement Cylinders (924G only)

Combination Valve (924G only)

FROMBRAKE/FAN

DRIVE SYSTEM

TO SECONDARYSTEERINGPRESSURE

SWITCH

MANIFOLD

SIGNAL FROMSTEERINGSYSTEM

X

TO STEERINGSYSTEM

FROMBRAKE

PISTONS

A

B

C

D

E

F

G

H

IJ

L

K

MN

STM

G 717

- 79-

Serviceman's H

andout No. 3

11/99Work Tool Hydraulic Components

Directions: Fill in the blank next to theletters with the correct component name.

A.

B.

C.

D.

E.

F.

G.

H.

I.

J.

K.

L.

M.

N.

SESV1717 Printed in U.S.A.11/99