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THE FUNCTION ISOLATION TOOLS ISOLATE
CIRCUITS FOR TRACING HYDRAULIC LINES
Function Isolation Tools
Grids On/Off
All Circuits Off
STANDARD VIEW
All Circuits On
021 (Orange) (Pilot Pump Output)
032 (Red) (Main Pump Output)
577 (Lt Green) (Drain/Return Line)
Machine Views
Machine View - Front
Machine View - Rear
Implement Stack
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021 (Orange) (Pilot Output)
CIRCUIT ISOLATED
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SYMBOLS AND DEFINITIONS PAGE
ELECTRICAL SYMBOLS
T
Pressure
Switch
Temperature
Switch
Level
Switch
Circuit Breaker
BASIC HYDRAULIC SYMBOLS
Fluid
Conditioner
Pump
or Motor
Spring
Variability
(Adjustable)
HOTKEYS (Keyboard Shortcuts)
VIEW ALL CALLOUTS
WHEN ONLY ONE CALLOUT IS SHOWING ON A
MACHINE VIEW, CLICKING ON THIS BUTTON WILL
MAKE ALL OF THE CALLOUTS VISIBLE. THIS
BUTTON IS TYPICALLY LOCATED IN THE TOP RIGHT
CORNER OF EVERY MACHINE VIEW PAGE.
© 2024 Caterpillar. All Rights Reserved. CAT, CATERPILLAR, LET’S DO THE
WORK, their respective logos, “Caterpillar Corporate Yellow”, the “Power Edge”
and Cat “Modern Hex” trade dress as well as corporate and product identity used
herein, are trademarks of Caterpillar and may not be used without permission.
Caterpillar: Non-Confidential.
FUNCTION
KEYS
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SCHEMATIC SYMBOLS AND DEFINITIONS
INTERNAL PASSAGEWAYS
VALVES
ENVELOPES
Two Position
One Position
Three Position
PORTS
Two-way
Three-Way
FLOW IN ONE
DIRECTION
FLOW ALLOWED IN
EITHER DIRECTION
Infinite
Positioning
Two
Position
PARALLEL
FLOW
PUMPS
Unidirectional
Three
Position
Unidirectional
CONTROL
AB
AB
Single Acting
Shifted Position
Normal Position
Spring
Loaded
Fluid
Conditioner
Spring
(Adjustable)
Spring
Pressure
Compensation
Control
Valves
Line Restriction
(Variable)
Restriction
Line Restriction
(Fixed)
Line Restriction
Variable and Pressure
Compensated
2-Section
Pump
Attachment
Pump: Variable and
Pressure Compensated
Bidirectional
MOTORS
Double Acting
Infinite Position
CHECK
Basic
Symbol
Variability
FIXED DISPLACEMENT
P T
P T
Pump
or Motor
Bidirectional
VARIABLE DISPLACEMENT
NON- COMPENSATED
CYLINDERS
Four-Way
BASIC HYDRAULIC
COMPONENT SYMBOLS
FIXED DISPLACEMENT
CROSS
FLOW
ACCUMULATORS
Shuttle
Unidirectional
Bidirectional
VARIABLE DISPLACEMENT
NON- COMPENSATED
Pilot
Controlled
Spring Loaded Gas Charged
Unidirectional
Bidirectional
PILOT CONTROL
RELEASED PRESSURE
External Return
ROTATING SHAFTS
Internal Return
Unidirectional
Bidirectional
REMOTE SUPPLY PRESSURE
Simplified
Complete
Internal
Supply Pressure
Hydraulic Pneumatic
Energy Triangles
COMBINATION CONTROLS
Solenoid
Solenoid
or Manual
Solenoid
and Pilot
Solenoid and
Pilot or Manual
MEASUREMENT
LINES
Servo
Thermal
Detent
Crossing
Joining
Manual Shutoff
General Manual
Push Button
Pedal
Spring
Vented
Pressurized
Transducer
(Fluid)
Transducer
(Gas / Air)
M
Generator
Electric
Motor
Pressure
Switch
Pressure Switch
(Adjustable)
Temperature
Switch
Electrical
Wire
Return Above Fluid Level
Temperature
Switch
Level
Switch
Flow
Switch
Wire, Cable, or Harness Assembly Identification:
Includes Harness Identification Letters and Harness
Connector Serialization Codes (see sample).
Switch (Normally Open): A switch that will close at a specified point (temp, press, etc.). The circle indicates
that the component has screw terminals and a wire can be disconnected from it.
Switch (Normally Closed): A switch that will open at a specified point (temp, press, etc.).
No circle indicates that the wire cannot be disconnected from the component.
AG-C4
111-7898
Part Number: for
Connector Plug
Plug
Ground (Case): This indicates that the component does not have a wire connected to ground.
It is grounded by being fastened to the machine.
Sender: A component that is used with a temperature or pressure gauge.
The sender measures the temperature or pressure.
Its resistance changes to give an indication to the gauge of the temperature or pressure.
Relay (Magnetic Switch): A relay is an electrical component that is activated by electricity.
It has a coil that makes an electromagnet when current flows through it.
The electromagnet can open or close the switch part of the relay.
Solenoid: A solenoid is an electrical component that is activated by electricity.
It has a coil that makes an electromagnet when current flows through it.
The electromagnet can open or close a valve or move a piece of metal that can do work.
Magnetic Latch Solenoid: An electrical component that is activated by electricity and held latched by a
permanent magnet. It has two coils (latch and unlatch) that make electromagnet
when current flows through them. It also has an internal switch that places
the latch coil circuit open at the time the coil latches.
1
L-C12
3E-5179
2
Ground (Wired): This indicates that the component is connected to a grounded wire.
The grounded wire is fastened to the machine.
Reed Switch: A switch whose contacts are controlled by a magnet. A magnet closes the contacts of
a normally open reed switch; it opens the contacts of a normally closed reed switch.
Circuit Breaker
HARNESS AND WIRE SYMBOLS
Fuse: A component in an electrical circuit that will open the circuit if too much current flows through it.
© 2024 Caterpillar. All Rights Reserved. CAT, CATERPILLAR, LET’S DO THE
WORK, their respective logos, “Caterpillar Corporate Yellow”, the “Power Edge”
and Cat “Modern Hex” trade dress as well as corporate and product identity used
herein, are trademarks of Caterpillar and may not be used without permission.
Caterpillar: Non-Confidential.
Return Below Fluid Level
T
Pressure
Switch
BASIC ELECTRICAL COMPONENT SYMBOLS
T
Flow
ELECTRICAL SYMBOLS
HYDRAULIC SYMBOLS - ELECTRICAL
G
Temperature
Pressure
FLUID STORAGE RESERVOIRS
MANUAL CONTROL
Push-pull Lever
MAIN AUX.
Receptacle
Pin or Socket Number
Harness Identification Letter(s): (A, B, C, AA, AB, AC, ...)
Harness Connector Serialization Code: The "C" stands for
"Connector" and the number indicates which connector in the
harness (C1, C2, C3, ...)
L-C12
3E-5179
5A
Fuse (5 Amps)
Harness identification code:
This example indicates wire group 325,
wire 135 in harness "AG".
Component
9X-1123
Part Number
325-AG135 PK-14
Wire Gauge*
Wire Color
*Wire gauge is shown in AWG (American Wire Gauge)
but could also be shown in metric denoted with mm
1
2
Deutsch connector: Typical representation
of a Deutsch connector. The plug contains all
sockets and the receptacle contains all pins.
1
2
Sure-Seal connector: Typical representation
of a Sure-Seal connector. The plug and receptacle
contain both pins and sockets.
M0132811-01
April 2024
966 and 972 Wheel Loader
Power Train System
RD61-UP
FGD1-UP
AH81-UP
WF91-UP
SM21-UP
WLW1-UP
EL91-UP
W991-UP
M7R1-UP
FFB1-UP
J8R1-UP
M7P1-UP
PUBLICATIONS.CAT.COM
© 2024 Caterpillar. All Rights Reserved. CAT, CATERPILLAR, LET’S DO THE WORK, their respective logos, “Caterpillar Corporate Yellow”, the “Power Edge”
and Cat “Modern Hex” trade dress as well as corporate and product identity used herein, are trademarks of Caterpillar and may not be used without permission.
Caterpillar: Non-Confidential
COMPONENT LOCATION
Schematic
Location
Machine
Location
Control Gp - Transmission
E-2
1
Cooler Gp - Transmission Oil
B-3
2
Filter Gp - Oil (Medium Pressure)
E-5
3
Pump Gp - Gear 2 Section Transmission
C-7
4
Screen Gp - Magnetic
A-5
5
Screen (Suction)
A-5
6
Sensor Gp - Temperature (Transmission Oil)
B-6
7
Sensor Gp - Speed (Torque Converter)
B-5
8
Torque Converter and Housing Group
C-5
9
Torque Converter GP
C-5
10
Transmission Ar
A-5
11
Valve Gp - Modulating (Lock Up Clutch)
D-4
12
Valve Gp - Modulating (Clutches)
E-2
13
Valve Gp - Relief (Torque Converter Inlet)
C-4
14
Valve Gp - Relief (Torque Converter Outlet)
C-4
15
Valve Gp - Solenoid
D-4
16
Description
TAP LOCATION
Tap
Number
P1A
Description
Schematic
Location
Pump Pressure Machine Test Location
E-6
P1B
Pump Pressure Transmission Test Location
D-4
P2A
Clutch 1 (Reverse) Pressure
E-3
P2B
Clutch 2 (Forward) Pressure
E-3
P2C
Clutch 3 (Fourth Speed) Pressure
D-3
P2D
Clutch 4 (Third Speed) Pressure
D-3
P2E
Clutch 5 (Second Speed) Pressure
C-3
P2F
Clutch 6 (First Speed) Pressure
C-3
P2
TC Inlet Pressure
D-4
P3
Lock Up Clutch Pressure
E-4
P4
TC Outlet Pressure
C-4
P5
Lube Pressure
B-3
7
6
5
P1A
4
3
2
(3) FILTER GP - OIL
(MEDIUM PRESSURE)
588-2590
1
(1) CONTROL GP
TRANSMISSION
508-8573 (966)
508-8574 (972)
P2A
E
P
C
CL1
(13) VALVE GP - MODULATING
(CLUTCHES)
244-3114
E
T
T
(12) VALVE GP - MODULATING
(LOCK UP CLUTCH)
244-3114
P2B
P3
P
C
CL2
T
T
VALVE GP-MDL
P2C
P
D
C
CL3
D
T
T
P2D
P2
P1B
CL4
P
C
F1
CONTROLS
CHARGING
(9) TORQUE CONVERTER AND
HOUSING GP
369-4088 (966)
367-3601 (972)
F2
T
T
(16) VALVE GP - SOLENOID
421-8199
F4
P2E
(14) VALVE GP - RELIEF
(TORQUE CONVERTER INLET)
148-1928
TC CHARGING
P
(4) PUMP GP
GEAR 2 SECTION TRANSMISSION
362-9555
(10) TORQUE CONVERTER GP
591-5089 (966)
591-5090 (972)
C
P2F
(15) VALVE GP - RELIEF
TORQUE CONVERTER OUTLET
592-4374
LOCK-UP
CLUTCH
(LUC)
CL5
T
T
C
C
P
C
CL6
SPEED
CLUTCHES ENGAGED
1F
2&6
2F
2&5
3F
2&4
4F
2&3
N
3
1R
1&6
2R
1&5
3R
4R
1&4
T
T
P4
F5
M0132811-01
16 Page, (Dimensions: 34 inches x 24 inches)
F3
(7) SENSOR GP
TEMPERATURE (TRANSMISSION OIL)
234-5013
(8) SENSOR GP
SPEED (TORQUE CONVERTER)
318-1179
F6
(2) COOLER GP
TRANSMISSION OIL
364-9906
1&3
LINE PATTERNS
B
B
Pressure Line
Pilot / Load Sensing Pressure
F7
Drain / Return Lines
Air Line
Component Group
CALLOUTS
P5
(11) TRANSMISSION AR
593-5119 (FOR PREFIXES AH8, WLW, M7R, EL9)
508-8568 (FOR PREFIXES RD6, J8R)
508-8569 (FOR PREFIXES FGD, WF9, SM2, W99, FFB, M7P)
Taps (Pressure, Sampling, Sensor - by letter)
YY
DL
DL
Callout Number
(6) SCREEN (SUCTION)
4S-8598
(Machine Location from
Component LocationsTable)
D
Connectors (By letter)
(52) VALVE GP - CONTROL
138-1234
Part Number
Component
Name
LUBE
(5) SCREEN GP - MAGNETIC
240-8259
POWER TRAIN CIRCUIT COLOR DESCRIPTIONS
TORQUE CONVERTER CHARGING
TORQUE CONVERTER OUTLET
SUPPLY LINE
DRAIN / RETURN LINE
CHARGING CONTROLS
A
Do not operate or work on this product unless you have
read and understood the instruction and warnings in the
relevant Operation and Maintenance Manuals and
relevant service literature. Failure to follow the instructions or heed the warnings could result in injury or
death. Proper care is your responsibility.
A
THIS SCHEMATIC IS FOR THE 966 AND 972 WHEEL LOADER
POWER TRAIN SYSTEM
MEDIA NUMBER: M0132811-01
SCHEMATIC PART NUMBER: 366-2621, CHANGE: 06, VERSION: -
SUMP
Components are shown installed on a fully operable machine with the key and engine off, transmission shifter
in neutral and with parking brake set.
Refer to the appropriate Service Manual for Troubleshooting, Specifications and Systems Operations.
Refer to the Parts Manual using a specific serial number prefix in SIS before ordering parts from this schematic.
7
6
5
4
3
2
1
POWER TRAIN LH VIEW
VIEW ALL CALLOUTS
P2C
P2B
P2A
8
P1B
P2
16
P2D
P2E
P2F
14
1
13
P3
12
POWER TRAIN RH VIEW
VIEW ALL CALLOUTS
15
2
9
10
P4
6
P5
5
11
3
4
P1A
7
0
