LOCKUP SOLENOID SHUTTLE VALVE OFF FROM PARKING BRAKE PUMP TO LOCKUP CLUTCH PRESSURE REDUCTION VALVE SELECTOR PISTON LOAD PISTON MODULATION REDUCTION VALVE LOAD PISTON ORIFICE LOCKUP CLUTCH VALVE
TORQUE CONVERTER DRIVE
777D Off Highway Truck
Adolfo
August 1997
III. POWER TRAIN
1. Components Layout
2. Operation
3. Maintenance
CHAPTER : Power Train
777D Off Highway Truck
III-2 Page: TORQUE CONVERTER LOCKUP MODULATION VALVE INLET AND
OUTLET RELIEF VALVES TORQUE CONVERTER FILTER TRANSMISSION OIL FILTER SOLENOIDS UPSHIFT DOWNSHIFT TRANSMISSION PUMP TRANSMISSION TORQUE CONVERTER AND TRANSMISSION OIL
TORQUE CONVERTER LOCKUP CLUTCH DRIVE SHAFT TRANSFER GEARS TRANSMISSION TRANSMISSION CONTROL VALVE TORQUE CONVERTER PUMP DIFFERENTIAL AND FINAL DRIVES
TYPICAL OFF-HIGHWAY TRUCK
POWER TRAIN
COMPONENT LOCATIONS
LOCKUP SOLENOID
III-3 Page: FREEWHEEL ASSEMBLY STATOR IMPELLER TURBINE LOCKUP PISTON TORQUE CONVERTER INLET OIL TORQUE CONVERTER LOCKUP OIL PASSAGE
CONVERTER DRIVE
TORQUE CONVERTER
ENGINE FLYWHEEL
TO TRANSFER GEARS
CHAPTER : Power Train
777D Off Highway Truck
III-4 Page: FREEWHEEL ASSEMBLY STATOR IMPELLER TURBINE LOCKUP PISTON TORQUE CONVERTER INLET OIL TORQUE CONVERTER LOCKUP OIL PASSAGE
DIRECT DRIVE
TORQUE CONVERTER
ENGINE FLYWHEEL TOTRANSFER GEARSCHAPTER : Power T
rain
777D Off Highway T
ruck
FROM PARKING BRAKE PUMP PRESSURE REDUCTION VALVE LOCKUP SOLENOID SHUTTLE VALVE SELECTOR PISTON LOAD PISTON MODULATION REDUCTION VALVE LOAD PISTON ORIFICE ON TO LOCKUP CLUTCH SHIMSCHAPTER : Power T
rain
777D Off Highway T
ruck
III-6 Page: FROM PARKING BRAKE PUMP TO LOCKUP CLUTCH PRESSURE REDUCTION VALVE LOCKUP SOLENOID SHUTTLE VALVE SELECTOR PISTON LOAD PISTON MODULATION REDUCTION VALVE LOAD PISTON ORIFICELOCKUP CLUTCH VALVE
DIRECT DRIVE
CHAPTER : Power T
rain
777D Off Highway T
ruck
PARKING BRAKE
RELEASE VALVE TORQUE
CONVERTER OUTLET RELIEF VALVE INLET RELIEF VALVE TO BRAKE COOLING CIRCUIT LOCKUP MODULATION VALVE OUTLET PRESSURE TAP BRAKE COOLING PRESSURE INLET PRESSURE CONVERTER CHARGING PUMP PARKING BRAKE RELEASE PUMP CONVERTER SCAVENGE PUMP LOCKUP CLUTCH
PILOT OIL PRESSURE
LOCKUP CLUTCH PRESSURE SCREEN PARKING BRAKE RELEASE PRESSURE TO BRAKE COOLING CIRCUIT LOCKUP SOLENOID LOCKUP CLUTCH LOCKUP REDUCING VALVE SHIMS PARKING BRAKE RELIEF VALVE
CHAPTER : Power T
rain
777D Off Highway T
ruck
III-8 Page: C DOWNSHIFT SOLENOID TANK CHARGING PUMP SCAVENGE PUMP FILTER ROTARY ACTUATOR SELECTOR VALVE GROUP ROTARY SELECTOR SPOOL PRIORITY REDUCTION VALVE LUBE RELIEF VALVE PUMP PRESSURE DOWNSHIFT PRESSURE PILOT OIL PRESSURE LUBE PRESSURE769D - 777D TRANSMISSION
HYDRAULIC SYSTEM
NEUTRAL UPSHIFT PRESSURE ON PRESSURE CONTROL GROUP TRANSMISSION CASE NEUTRALIZER VALVE RELIEF VALVE OIL COOLER UPSHIFT SOLENOID A B D E F G HIII-9 Page: ROTARY SELECTOR SPOOL NEUTRALIZER VALVE PRIORITY REDUCTION VALVE TRANSM. LUBE RELIEF VALVE RELIEF VALVE LUBRICATION PRESSURE PILOT OIL PRESSURE SCREEN
769D - 777D TRANSMISSION SELECTOR VALVE
GROUP
CHAPTER : Power Train
777D Off Highway Truck
III-10 Page: ROTARY SELECTOR SPOOL PRIORITY REDUCTION VALVE LUBE RELIEF VALVE RELIEF VALVE LUBRICATION PRESSURE PILOT OIL PRESSURE SCREEN
769C - 777C TRANSMISSION SELECTOR VALVE
GROUP
STARTING IN FIRST SPEED FORWARD
NEUTRALIZER VALVE
III-11 Page:
C
A
B
D
E
F
G
H
769D - 777D PRESSURE
CONTROL GROUP
NEUTRAL
CHAPTER : Power T
rain
777D Off Highway T
ruck
III-12 Page: SELECTOR PISTON LOAD PISTON DECAY ORIFICE LOAD PISTON PLUGPILOT OIL PASSAGE FROM PUMP TO CLUTCH MODULATION REDUCTION VALVE LOAD PISTON ORIFICE BALL CHECK VALVE
PLUG
CLUTCH PRESSURE TAP SLUG
VALVE STATION
III-13 Page:
VALVE STATION
CHAPTER : Power Train
777D Off Highway Truck
III-14 Page:
VALVE STATION
III-15 Page:
VALVE STATION
CLUTCH DECAY
DECAY ORIFICECHAPTER : Power T
rain
777D Off Highway T
ruck
III-16 Page: FILTER DOWNSHIFT SOLENOID TANK CHARGING PUMP SCAVENGE PUMP ROTARY ACTUATOR SELECTOR VALVE GROUP ROTARY SELECTOR SPOOL PRIORITY REDUCTION VALVE LUBE RELIEF VALVE PUMP PRESSURE DOWNSHIFT PRESSURE PILOT OIL PRESSURE LUBE PRESSURE UPSHIFT PRESSURE TRANSMISSION CASE NEUTRALIZER VALVE RELIEF VALVE OIL COOLER UPSHIFT SOLENOID A B D E F G H C PRESSURE CONTROL GROUP769C - 777C TRANSMISSION
HYDRAULIC SYSTEM
III-17 Page:
VALVE STATION
PRIMARY PRESSURE
LOAD PISTON
PLUG (REMOVED)
CHAPTER : Power T
rain
777D Off Highway T
ruck
III-18 Page:777D SHIFT MODULATION CYCLE
THIRD(3&6) TO FOURTH (1&5)
NORMAL SHIFT CYCLE
COMPLETE CLUTCH ENGAGEMENT
INITIAL CLUTCH ENGAGEMENT
NORMAL CLUTCH SLIP PRIMARY
PRESSURE
FILL TIME
TIME
418 373 353 265 50 0 CLUTCH 5 CLUTCH 1 CLUTCH 3 CLUTCH 6
PRESSURE
CHAPTER : Power T
rain
777D Off Highway T
ruck
777C SHIFT MODULATION CYCLE
SECOND TO THIRD
NORMAL SHIFT CYCLE
COMPLETE CLUTCH ENGAGEMENT
INITIAL CLUTCH ENGAGEMENT
NORMAL CLUTCH SLIP PRIMARY
PRESSURE
FILL TIME
TIME
418 373 265 80 0 CLUTCH 1 CLUTCH 3 CLUTCH 6
PRESSURE
CHAPTER : Power T
rain
777D Off Highway T
ruck
III-20 Page: COMPLETE CLUTCH ENGAGEMENT INITIAL CLUTCH ENGAGEMENT NORMAL CLUTCH SLIPHIGH PRIMARY PRESSURE - HARSH SHIFT
LOW PRIMARY PRESSURE - CLUTCH SLIPPING
HIGH PRIMARY PRESSURE
RESTRICTED LOAD PISTON ORIFICE SLOW MODULATION
TIME
NORMAL PRIMARY PRESSURE LOW PRIMARY PRESSURESHIFT MODULATION
PROBLEMS
PRESSURE
0
P1RESTRICTED LOAD PISTON ORIFICE
III-21 Page:
Lab A: Component Location and Identification Worksheet I
769D - 777D Off-highway Trucks Torque Converter Hydraulic System
Directions: Refer to the Lab A Handout Illustration Worksheet V. Place the correct letter or number
next to the component. During the slide presentation, use this sheet to take notes on the function of each component.
______ Torque Converter - example: Located on the rear of the engine. Provides a fluid coupling
between the engine and the transmission and multiplies torque. Contains a lockup clutch for more efficient operation.
______ Torque Converter Pump (1. Scavenge, 2. Charging, and 3. Park Brake Release) -
______ Torque Converter Scavenge Screen -
______ Torque Converter Charging Filter -
______ Torque Converter Inlet Relief Valve -
______ Torque Converter Outlet Relief Valve -
______ Torque Converter Lockup Clutch Valve
-______ Parking Brake Release Valve -
______ Parking Brake Release Filter -
CHAPTER : Power Train
777D Off Highway Truck
III-22 Page:
LAB EXERCISES
Lab A: Component Location and Identification Worksheet ID
769D - 777D Off-highway Trucks Transmission Hydraulic System
Directions: Refer to the Lab A Handout Illustration Worksheet V. Place the correct letter or number
next to the component. During the slide presentation, use this sheet to take notes on the function of each component.
______ Transmission Tank - example: Located on the left side of the truck. Contains a sight gauge for
checking power train hydraulic level.
______ Transmission Pump -
______ Transmission Filter
-______ Transmission Magnetic Suction Screen -
______ Transmission Oil Cooler -
______ Transmission Control Valve -
______ Upshift Solenoid Valve -
III-23 Page:
TYPICAL OFF-HIGHWAY TRUCK
POWER TRAIN
COMPONENT LOCATIONS
Lab A: Component Location and Identification Worksheet V
CHAPTER : Power T
rain
777D Off Highway T
ruck
III-24 Page:LAB EXERCISES
TO BRAKE COOLING CIRCUIT TO BRAKE COOLING CIRCUIT7. Inlet Relief Valve
8. Lockup Modulation Valve 9. Scavenge Pump
10. Lockup Solenoid 11. Shuttle Valve 12. Lockup Clutch
Lab B: Torque Converter
Hydraulic System
Component Identification
Worksheet I: (769D - 777D)
Identify Test Ports
A. Inlet Pressure
B. Parking Brake Release Pressure C. Lockup Clutch Pressure
D. Outlet Pressure E. Pilot Pressure
Identify Components
1. Outlet Relief Valve
2. Parking Brake Release Valve 3. Converter Charging Pump 4. Torque Converter
5. Lockup Reducing Valve 6. Parking Brake Release Pump
Directions: Write the letter
or number of the item in the correct blank on the
III-25 Page:
Lab C: Torque Converter Hydraulic System Testing
Shop Lab Exercise
Procedure:
Perform the following tests listed in the Power Train Testing and Adjusting Service Manual Module for the lab machine used:
• Visual Checks (8) for the hydraulic system which include Brake Cooling, Torque Converter, and Hoist Hydraulic Systems • Torque Converter Outlet Pressure
• Torque Converter Inlet Pressure • Parking Brake Release Pressure • Lockup Clutch Pilot Pressure • Lockup Clutch Leakage
• Lockup Clutch Signal Pressure (785B - 793B) • Lockup Clutch Maximum Pressure
• Lockup Clutch Primary Pressure Class notes
Lab D Worksheets (I and II) Off-highway Truck
Mechanic's tools
The following test equipment:
1 - 8T0854 Gauge 1000 kPa (145 psi) 1 - 8T0850 Gauge 4000 kPa (580 psi) 1 - 8T0851 Gauge 16000 kPa (2300 psi) 1 - 6V3965 Nipple
1 - 6V4143 Valved Coupler 1 - 6V3079 Diagnostic Hose 1 - 6V3121 Multitach Group
1 - Oil container [approximately 19 l (5 gal.) capacity] 1 - Special Instruction "6V3121 Multitach Group" (Form
CHAPTER : Power Train
777D Off Highway Truck
III-26 Page:
LAB EXERCISES
______ Check 1 - Oil levels in the hydraulic tank ______ Check 2 - External Leakage
______ Check 3 - Parking brake release oil filter ______ Check 4 - Torque converter oil filter
Machine Model______________________ Name/Code _________________________ Machine PIN (S/N)___________________ Transmission S/N ____________________ Engine S/N _________________________ S.M.H. ____________________________ Dealer ______________________________ Customer ___________________________ Job ________________________________ Application __________________________ Date _______________________________ Serviceman __________________________
VISUAL CHECKS
TEST SPECS ACTUAL
Torque Converter Outlet Pressure at Stall Torque Converter Stall Speed
Torque Converter Inlet Pressure Lockup Clutch Pilot Pressure Parking Brake Release Pressure Lockup Clutch Leakage
Lockup Clutch Maximum Pressure Lockup Clutch Primary Pressure
______ Check 5 - Torque converter scavenge screen ______ Check 6 - Oil cooler screens
______ Check 7 - Components inside hydraulic tank ______ Check 8 - Inspect return oil screen
Lab C: Torque Converter Hydraulic System Testing
769C - 777C Off-highway Trucks - Worksheet I
Directions: Use this sheet to check off each of the steps listed in the Power Train Testing and
CHAPTER : Power T
rain
777D Off Highway T
ruck
III-27 Page:LAB EXERCISES
TO BRAKE COOLING CIRCUIT TO BRAKE COOLING CIRCUIT769D - 777D TORQUE
CONVERTER
HYDRAULIC SYSTEM
TORQUE CONVERTER
DRIVE
CHAPTER : Power T
rain
777D Off Highway T
ruck
III-28 Page:LAB EXERCISES
Lab D: Tracing Torque Converter Oil System Flow (769D - 777D)
Worksheet II
Directions: Trace the flow of oil during the condition listed below using different colored pencils to show each path.
TO BRAKE COOLING CIRCUIT TO BRAKE COOLING CIRCUIT
769C - 777C TORQUE CONVERTER
HYDRAULIC SYSTEM
DIRECT DRIVE
III-29 Page:
Lab E: Torque Converter Hydraulic System Operation
(769D - 777D) Worksheet IDirections: Circle the letter of the correct statement that completes the sentence. Example: Torque converter leakage oil is removed from the torque converter by the:
A. Parking brake release pump B. Scavenge pump
C. Charging pump
5. When the lockup solenoid opens and the shuttle valve moves, the shuttle valve:
A. opens a passage to drain B. closes a passage to drain
C. directs lockup clutch oil to the lockup clutch 6. Torque converter operating pressure is
maintained by the: A. inlet relief valve B. outlet relief valve
C. parking brake release valve
7. Modulation of the lockup clutch is determined by the:
A. load piston
B. modulation reducing valve C. load piston orifice
1. The torque converter is in direct drive in the following speeds:
A. REVERSE and FIRST
B. second half of FIRST through SEVENTH C. NEUTRAL to FIRST
2. If the torque converter lockup solenoid does not receive an electrical signal in SECOND SPEED FORWARD, the torque converter will:
A. stay in DIRECT DRIVE B. go to DIRECT DRIVE
C. go to TORQUE CONVERTER DRIVE 3. The source of torque converter lockup oil is
from the:
A. transmission charging pump B. torque converter charging pump C. parking brake release pump
4. Excess oil pressure to the torque converter during a cold start-up is prevented by the _______.
A. inlet relief valve B. outlet relief valve
CHAPTER : Power T
rain
777D Off Highway T
ruck
III-30 Page:LAB EXERCISES
C A B D E F G H ONLab F: Transmission
Hydraulic System
Component
Identification
(769D - 777D)
Worksheet I
Directions: Write the letter or
number of the item in the correct blank on the schematic.
Identify Test Ports
A. Downshift Pressure B. Pump Pressure C. Lube Pressure D. Upshift Pressure E. Pilot Pressure Identify Components 1. Charging Pump
2. Pressure Control Group 3. Rotary Selector Spool 4. Upshift Solenoid 5. Lube Relief Valve
12. Neutralizer valve 13. Oil Cooler 14. Filter 15. Screen
16. A to C and E to H 6. Priority Reduction Valve
7. Main Relief Valve 8. Scavenge Pump 9. Downshift Solenoid 10. Rotary Actuator 11. Selector Valve Group
CHAPTER : Power T
rain
777D Off Highway T
ruck
III-31 Page:LAB EXERCISES
FROM PUMP TO CLUTCHIdentify Test Ports
A. Primary and Clutch Pressures B. Pilot Pressure
Identify Components
1. Ball Check Valve 2. Selector Piston 3. Load Piston Plug 4. Pilot Oil Passage 5. Pin
6. Pilot Oil Plug
7. Load Piston Orifice 8. Load Piston
9. Decay Orifice 10. Clutch Pressure Tap 11. Slug
12. Modulation Reduction Valve
Pressure Control Group Valve Station Worksheet III
Directions: Write the
letter or number of the item in the correct blank on the schematic.
CHAPTER : Power Train
777D Off Highway Truck
III-32 Page:
LAB EXERCISES
Lab G: Transmission Hydraulic System Testing
Shop Lab Exercise
Procedures:
Perform the following tests listed in the Power Train Testing and Adjusting Service Manual Module for the lab machine used:
• Visual Checks (6)
• Transmission Pump Pressure • Transmission Lubrication Pressure • Pilot Pressure
• Pressure Control Group Clutch Pressures • Primary Clutch Pressures
• Dual Stage Relief Valve Pressure Class notes
Lab G Worksheets (I and II) Off-highway Truck
Mechanic's tools
The following test equipment:
1 - 1U5481 Pressure Gauge Group 1 - 1U5482 Pressure Adaptor Group 1 - 3B7282 Nipple
1 - 3B6552 Nipple
1 - 6V4142 Unvalved Nipple
III-33 Page:
Lab G: Transmission Hydraulic System Testing
769D - 793C Off-highway Trucks - Worksheet I
Directions: Use this sheet to check off each of the steps listed in the Power Train Testing and Adjusting
Service Manual Module. All tests should be run with the transmission in NEUTRAL. Machine Model______________________ Name/Code _________________________ Machine PIN (S/N)___________________ Transmission S/N ____________________ Engine S/N _________________________ S.M.H. ____________________________ Dealer ______________________________ Customer ___________________________ Job ________________________________ Application __________________________ Date _______________________________ Serviceman __________________________
______ Check 5 - Transmission case oil quantity ______ Check 6 - Transmission oil tank debris ______ Check 1 - Oil levels in the hydraulic tank
______ Check 2 - External leakage ______ Check 3 - Oil filter examination ______ Check 4 - Magnetic screen debris
VISUAL CHECKS
DU AL S TAGE RELIEF LOCKU P CLU TCH DEACTIVATED S PECS ACTU AL LOW IDLE HIGH IDLE LOW IDLE HIGH IDLE PU MP PRES S U RE
DU AL S TAGE RELIEF LOCKU P CLU TCH ACTIVATED S PECS ACTU AL LOW IDLE HIGH IDLE LOW IDLE HIGH IDLE PU MP PRES S U RE S PECS ACTU AL LOW IDLE HIGH IDLE LOW IDLE HIGH IDLE PILOT PRES S U RE N O N O LU BE PRES S U RE
CHAPTER : Power Train
777D Off Highway Truck
III-34 Page:
LAB EXERCISES
Lab G: Transmission Hydraulic System Testing
769D - 793C Off-highway Trucks - Worksheet II
Directions: Use this sheet to check off each of the steps listed in the Power Train Testing and Adjusting
Service Manual Module.
CLU TCH CHART N R 1 2 3 4 5 6 7
PRIMARY CLU TCH PRES S U RE AT LOW IDLE
(LOAD PIS TON PLU G REMOVED)
STATION CLUTCH SPECS ACTUAL A B C D E F G H
PRIMARY CLU TCH PRES S U RE AT LOW IDLE (LOAD PIS TON PLU G IN S TALLED)
S PECS ACTU AL S TATION CLU TCH LOW
IDLE HIGH IDLE LOW IDLE HIGH IDLE A B C D E F G H
III-35 Page:
1. Load Piston 2. Pilot Oil Passage 3. Decay Orifice 4. Load Piston Plug 5. Modulation Reduction
Valve
6. Load Piston Orifice 7. Ball Check Valve 8. Clutch Pressure Tap 9. Pilot Pressure Plug 10. Selector Piston 11. Slug
As this component moves and closes a drain passage, modulation will begin
Removal of this component allows the technician to check pilot pressure
Allows oil from the rotary selector spool to move the selector piston
Controls the rate of clutch engagement
Works with the modulation reduction valve to control clutch pressure
Allows clutch pressure to be directed into the center chamber of the modulation reduction valve
Allows the technician to check clutch pressure
Removal of this component causes the clutch pressure to remain at the primary pressure
Controls the rate of clutch release
Works with load piston to control clutch pressure
Directions: Modified True/False. If a statement is false, underline or circle the word or words that
make the statement incorrect and replace with word(s) to make the statement correct. (Each question is worth 2 points.)
a transmission Example: F 1. This is an engine class.
1. To initiate clutch filling, pilot oil moves the selector piston.
2. The size of the modulation reducing valve determines the rate of clutch modulation. 3. To check the primary clutch pressure, remove the load piston plug.
4. Pins in a clutch station increase the modulation time. 5. Clutch release time is determined by the decay orifice.
CHAPTER : Power T
rain
777D Off Highway T
ruck
III-36 Page:POSTTEST
VALVE STATION
FROM PUMP TO CLUTCH Test Ports Primary Pressure Pilot Pressure Clutch Pressure Components Load Piston Pilot Oil Passage Decay Orifice Load Piston Plug Modulation ReductionValve
Load Piston Orifice Ball Check Valve Clutch Pressure Tap Pilot Oil Plug Selector Piston Slug
Pin
Directions: Match the
components and test ports with the associated number or letter.
(Each question is worth 1 point.)
13
15
14
10
11
7
9
3
12
8
4
6
5
2
1
III-37 Page:
Directions: Use the schematic on page 38. After each statement, circle the correct sequence of events
that occurs.
Example: The operator makes a shift from NEUTRAL to FIRST FORWARD.
A. 1-Pilot oil moves selector piston
2-Selector piston closes drain
3-Load piston moves reducing valve 4-Modulation begins
B. 1-Selector piston closes drain
2-Pilot oil moves selector piston 3-Modulation begins 4-Load piston moves
reducing valve
A. 1-Rotary selector spool opens pilot oil passage to drain
2-Load piston oil is directed through decay orifice
3-Selector piston opens drain
A. 1-Pump oil is directed through load piston orifice
2-Pump oil is directed to clutch
3-Modulation reduction valve moves
B. 1-Pump oil is directed to clutch
2-Modulation reduction valve moves
3-Pump oil is directed through load piston orifice
C. 1-Modulation reduction valve moves
2-Pump oil is directed to clutch
3-Pump oil is directed through load piston orifice
B. 1-Rotary selector spool opens pilot oil passage to drain
2-Selector piston opens drain
3-Load piston oil is directed through decay orifice
C. 1-Selector piston opens drain
2-Load piston oil is directed through decay orifice
3-Rotary selector spool opens pilot oil passage to drain
C. 1-Modulation begins 2-Load piston moves
reducing valve
3-Selector piston closes drain
4-Pilot oil moves selector piston
CHAPTER : Power Train
777D Off Highway Truck
III-38 Page:
POSTTEST
Torque Converter Hydraulic System Posttest
(769D - 777D)
Directions: Match the component to its primary function.
Maintains high oil pressure to the lockup reducing valve Supplies oil for hydraulic energy transfer
Maintains working pressure within the torque converter When energized, supplies pilot oil to initiate direct drive Relieves excess pressure to the torque converter
Provides a controlled rate of engagement of the lockup clutch
Transfers engine power to the transmission Reduces pump supply pressure to pilot pressure Supplies oil to the lockup clutch
Directions: Modified True/False. If a statement is false, underline or circle the word or words that
make the statement incorrect and replace with word(s) to make the statement correct.
a power train Example: F 1. This is an engine class.
1. The inlet relief valve controls the maximum pressure in the torque converter. 2. The parking brake release pump supplies oil to the lockup modulation valve. 3. Lockup clutch oil pressure is controlled by the parking brake release valve.
4. Transmission oil pressure is used to pressurize the torque converter lockup clutch when the torque converter is in direct drive.
5. When the transmission is in REVERSE, the torque converter is in direct drive. 6. Direct drive is in gears FIRST through SEVENTH.
1. Lockup Solenoid 2. Inlet Relief Valve 3. Torque Converter 4. Lockup Reducing Valve 5. Parking Brake Release
Valve
6. Outlet Relief Valve 7. Lockup Modulation Valve 8. Converter Charging Pump 9. Diverter Valve
10. Parking Brake Release Pump
CHAPTER : Power T
rain
777D Off Highway T
ruck
III-39 Page:POSTTEST
Parking Brake Release Pressure
Pilot Pressure Outlet Pressure Inlet Pressure
Lockup Clutch Pressure
Components
Lockup Solenoid Inlet Relief Valve Torque Converter Lockup Reducing Valve Parking Brake Release Valve
Outlet Relief Valve Lockup Modulation Valve Converter Charging Pump Scavenge Pump
Parking Brake Release Pump Shuttle Valve 2 4 1 7 TO BRAKE COOLING CIRCUIT 5 8 D A 3 6 9 E C B TO BRAKE COOLING CIRCUIT 10 11 769D - 777D TORQUE CONVERTER HYDRAULIC SYSTEM 12
CHAPTER : Power Train
777D Off Highway Truck
III-40 Page:
POSTTEST
Directions: Use the schematic on page 41. After each statement, circle the correct sequence of events
that occurs.
Example: The operator makes a shift from NEUTRAL to FIRST FORWARD and the ground speed
increases.
A. 1-Torque converter is in TC drive
2-Ground speed increases and the lockup clutch modulation valve is activated
3-Lockup clutch engages
B. 1-Lockup clutch engages 2-Ground speed
increases and the lockup clutch modulation valve is activated 3-Torque converter is in TC drive C. 1-Ground speed increases and the lockup clutch modulation valve is activated
2-Lockup clutch engages 3-Torque converter is in
TC drive
C. 1-Parking brake release pump directs oil to lockup reducing valve 2-Pilot oil directed to
lockup solenoid valve 3-Parking brake release oil directed to lockup modulation valve spool A. 1-Parking brake release
oil directed to lockup modulation valve spool 2-Pilot oil directed to
lockup solenoid valve 3-Parking brake release
pump directs oil to lockup reducing valve
B. 1-Parking brake release oil directed to lockup modulation valve spool 2-Parking brake release
pump directs oil to lockup reducing valve 3-Pilot oil directed to
lockup solenoid valve
B. 1-Lockup solenoid valve opens
2-Shuttle valve moves and blocks drain 3-Load piston moves A. 1-Shuttle valve moves
and blocks drain 2-Load piston moves 3-Lockup solenoid valve
opens
C. 1-Load piston moves 2-Lockup solenoid valve
opens
3-Shuttle valve moves and blocks drain
A. 1-Shuttle valve moves and opens drain
2-Lockup solenoid valve closes
3-Load piston moves
C. 1-Lockup solenoid valve closes
2-Shuttle valve moves and opens drain 3-Load piston moves B. 1-Load piston moves
2-Shuttle valve moves and opens drain
3-Lockup solenoid valve closes
III-41 Page:
1. Charging Pump
2. Pressure Control Group 3. Rotary Selector Spool 4. Upshift Solenoid 5. Oil Cooler Relief Valve 6. Priority Reduction Valve 7. Main Relief Valve 8. Scavenge Pump 9. Downshift Solenoid 10. Rotary Actuator 11. Selector Valve Group 12. Neutralizer Valve 13. Oil Cooler 14. Filter 15. Manifold 16. A through H Regulates pressure inside oil cooler
Reduces temperature of transmission oil Removes oil from transmission case Maintains pilot oil pressure
Removes debris from transmission oil Supplies modulated pressures to clutches
Directs oil to move rotary actuator vane clockwise Maintains maximum system pressure
Chooses appropriate clutch combinations for each speed Six valve clutch stations
Moves rotary selector spool
Keeps machine from moving if transmission is started in gear
Supplies oil to all clutches
Directs oil to move rotary actuator vane counterclockwise
Maintains and directs oil pressures to the pressure control group
CHAPTER : Power Train
777D Off Highway Truck
III-42 Page:
POSTTEST
Directions: Modified True/False. If a statement is false, underline or circle the word or words that
make the statement incorrect and replace with word(s) to make the statement correct.
a transmission Example: F 1. This is an electrical test.
1. In NEUTRAL, no clutches are engaged.
2. If the machine is started IN GEAR, the neutralizer valve stops the flow of pilot oil. 3. Clutch pressure is maintained by the relief valve.
4. Reverse is an upshift.
5. During a shift, clutches are always drained and then refilled. 6. REVERSE and the first half of FIRST are torque converter drive.
CHAPTER : Power T
rain
777D Off Highway T
ruck
III-43 Page:POSTTEST
Lube Pressure Components Scavenge PumpPriority Reduction Valve Rotary Selector Spool Neutralizer Valve Lube Relief Valve A to C and E to H Pressure Control Group Main Relief Valve Charging Pump Downshift Solenoid Filter
Selector Valve Group Upshift Solenoid Oil Cooler Rotary Actuator Screen C 8 13 9 4 1 14 10 11 3 12 6 5 7 A B D E F G H B A E C D ON 2 15 16 769D- 777D TRANSMISSION HYDRAULIC SYSTEM
CHAPTER : Power Train
777D Off Highway Truck
III-44 Page:
Directions: Use the schematic on page 45. After each statement, circle the correct sequence of events
that occurs.
Example: The operator has moved the shift lever from NEUTRAL to FIRST FORWARD.
A. 1-Downshift solenoid is de-energized
2-Upshift solenoid is energized
3-Rotary actuator moves to FIRST SPEED FORWARD
B. 1-Rotary actuator moves to FIRST SPEED FORWARD 2-Downshift solenoid is de-energized 3-Upshift solenoid is energized C. 1-Upshift solenoid is energized
2-Rotary actuator moves to FIRST SPEED FORWARD
3-Downshift solenoid is de-energized
1. The engine is started with the transmission in NEUTRAL.
2. The engine is started with the gear shift lever in FIRST SPEED FORWARD.
3. During an upshift, the following occurs: A. 1-Neutralizer valve
moves
2-Pilot oil flows through rotary selector spool to one station
3-Downshift solenoid is energized
B. 1-Pilot oil flows through rotary selector spool to one station 2-Downshift solenoid is energized 3-Neutralizer valve moves C. 1-Downshift solenoid is energized 2-Neutralizer valve moves
3-Pilot oil flows through rotary selector spool to one station
A. 1-Charge pump oil flows to priority reduction valve
2-Pilot oil flows to neutralizer valve 3-Rotary selector spool
blocks charge pump oil to neutralizer valve
C. 1-Pilot oil flows to neutralizer valve 2-Rotary selector spool
blocks charge pump oil to neutralizer valve 3-Charge pump oil flows
to priority reduction valve
B. 1-Rotary selector spool blocks charge pump oil to neutralizer valve 2-Pilot oil flows to
neutralizer valve 3-Charge pump oil flows
to priority reduction valve
A. 1-Charge pump moves the upshift valve 2-Upshift solenoid is
energized
3-Rotary actuator oil moves the downshift valve
B. 1-Upshift solenoid is energized
2-Charge pump oil moves the rotary actuator
3-Rotary actuator moves the rotary selector spool
C. 1-Rotary actuator oil moves the downshift valve
2-Upshift solenoid is energized
3-Charge pump moves the upshift valve
III-45 Page:
rotary actuator.
1. On some ICM transmissions, the Dual Stage Relief Valve is activated T F
during torque converter lockup.
2. On all ICM transmission controls, REVERSE is an upshift from T F
NEUTRAL and the downshift solenoid is activated whenever the shift lever is in NEUTRAL.
3. When the transmission shift lever is in a speed other than NEUTRAL, T F
the rotary selector spool provides a path to drain for two clutches.
4. On all ICM transmission controls, the priority reduction valve controls T F
the pressure of the "pilot oil" that is used to shift the selector piston in each station.
5. The load piston orifice in an ICM transmission is a "cascade-type" and T F
controls the modulation of clutch engagement.
6. In an ICM transmission, the "primary pressure setting" in each station T F
can cause harsh shifts when too low and clutch slipping when too high.
7. The "primary pressure settings" are the same for all ICM clutch stations. T F
8. Final clutch pressure is adjusted with shims. T F
9. If the "primary pressure setting" is correct and the final clutch pressure T F
is low, the load piston springs should be replaced.
10. When manually rotating the rotary selector spool with the engine T F