03PTRAIN

LOCKUPSOLENOID

SHUTTLEVALVE

OFF

FROMPARKING BRAKE

PUMP

TOLOCKUPCLUTCH

PRESSUREREDUCTION

VALVE

SELECTORPISTON

LOADPISTON

MODULATIONREDUCTION

VALVE

LOAD PISTONORIFICE

LOCKUP CLUTCH VALVETORQUE CONVERTER DRIVE

Service TrainingMALAGA

777D Off Highway Truck

AdolfoAugust 1997

III. POWER TRAIN

1. Components Layout2. Operation3. Maintenance4. Testing & Adjusting

CHAPTER : Power Train


III-2Page:

TORQUECONVERTER

LOCKUPMODULATION

VALVE

INLET ANDOUTLET RELIEF VALVES

TORQUECONVERTER FILTER

TRANSMISSIONOIL FILTER

SOLENOIDSUPSHIFT

DOWNSHIFT

TRANSMISSIONPUMP

TRANSMISSION

TORQUE CONVERTERAND TRANSMISSION OIL

TORQUECONVERTER

LOCKUPCLUTCH

DRIVESHAFT

TRANSFERGEARS

TRANSMISSION

TRANSMISSIONCONTROL VALVE

TORQUECONVERTER

PUMP

DIFFERENTIAL ANDFINAL DRIVES

TYPICAL OFF-HIGHWAY TRUCKPOWER TRAIN

COMPONENT LOCATIONS

LOCKUPSOLENOID



III-3Page:

FREEWHEELASSEMBLY

STATOR

IMPELLER

TURBINE

LOCKUP PISTON

TORQUE CONVERTERINLET OIL

TORQUE CONVERTERLOCKUP OIL PASSAGE

CONVERTER DRIVETORQUE CONVERTER

EN

GIN

E F

LYW

HE

EL

TO TRANSFER GEARS



III-4Page:

FREEWHEELASSEMBLY

STATOR

IMPELLER

TURBINE

LOCKUPPISTON

TORQUECONVERTER

INLET OIL

TORQUECONVERTERLOCKUP OIL

PASSAGE

DIRECT DRIVETORQUE CONVERTER

EN

GIN

E F

LYW

HE

EL

TOTRANSFERGEARS

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III-5P

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FROMPARKING BRAKE

PUMP

PRESSUREREDUCTION

VALVE

LOCKUPSOLENOID

SHUTTLEVALVE

SELECTORPISTON

LOADPISTON

MODULATIONREDUCTION

VALVE

LOAD PISTONORIFICE

ON

TOLOCKUPCLUTCH

SHIMS

LOCKUP CLUTCH VALVECLUTCH FILLING

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FROMPARKING BRAKE

PUMP

TOLOCKUPCLUTCH

PRESSUREREDUCTION

VALVELOCKUP

SOLENOID

SHUTTLEVALVE

SELECTORPISTONLOAD

PISTON

MODULATIONREDUCTION

VALVE

LOAD PISTONORIFICE

LOCKUP CLUTCH VALVEDIRECT DRIVE

ON

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PARKING BRAKERELEASE VALVE TORQUE

CONVERTER

OUTLETRELIEF VALVE

INLETRELIEF VALVE

TO BRAKECOOLINGCIRCUIT

LOCKUPMODULATION

VALVE

OUTLETPRESSURE

TAP

BRAKE COOLINGPRESSURE

INLETPRESSURE

CONVERTERCHARGING

PUMP

PARKINGBRAKE

RELEASEPUMP

CONVERTERSCAVENGE

PUMP

LOCKUP CLUTCHPILOT OIL PRESSURE

LOCKUP CLUTCHPRESSURE

SCREEN

PARKING BRAKERELEASE PRESSURE

TO BRAKECOOLING CIRCUIT

LOCKUPSOLENOID

LOCKUPCLUTCH

LOCKUPREDUCING

VALVE

SHIMS

PARKING BRAKERELIEF VALVE

769D - 777D TORQUE CONVERTER HYDRAULIC SYSTEMNEUTRAL

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C

DOWNSHIFTSOLENOID

TANK

CHARGINGPUMP SCAVENGE

PUMP

FILTERROTARY

ACTUATOR

SELECTOR VALVEGROUP

ROTARYSELECTOR

SPOOL

PRIORITYREDUCTION

VALVE

LUBERELIEF VALVE

PUMPPRESSURE

DOWNSHIFTPRESSURE

PILOT OILPRESSURE

LUBEPRESSURE

769D - 777D TRANSMISSIONHYDRAULIC SYSTEM

NEUTRAL

UPSHIFTPRESSURE

ON

PRESSURE CONTROLGROUP

TRANSMISSIONCASE

NEUTRALIZERVALVE

RELIEFVALVE

OIL COOLER

UPSHIFTSOLENOID

A

B

D

E

F

G

H



III-9Page:

ROTARYSELECTOR

SPOOL

NEUTRALIZERVALVE

PRIORITYREDUCTION

VALVE

TRANSM.LUBE

RELIEFVALVE

RELIEFVALVE

LUBRICATIONPRESSURE

PILOTOIL

PRESSURE

SCREEN

769D - 777D TRANSMISSION SELECTOR VALVEGROUPNEUTRAL



III-10Page:

ROTARYSELECTOR

SPOOL

PRIORITYREDUCTION

VALVE

LUBERELIEFVALVE

RELIEFVALVE

LUBRICATIONPRESSURE

PILOT OILPRESSURE

SCREEN

769C - 777C TRANSMISSION SELECTOR VALVEGROUP

STARTING IN FIRST SPEED FORWARD

NEUTRALIZERVALVE



III-11Page:

C

A

B

D

E

F

G

H

769D - 777D PRESSURECONTROL GROUP

NEUTRAL

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III-12P

age:

SELECTOR PISTON

LOAD PISTON

DECAY ORIFICE

LOAD PISTON PLUG

PILOT OILPASSAGE

FROM PUMPTO CLUTCH

MODULATIONREDUCTION

VALVE

LOAD PISTONORIFICE

BALL CHECK VALVE

PLUG

CLUTCH PRESSURE TAP

SLUG

VALVE STATIONCLUTCH RELEASED



III-13Page:

VALVE STATIONCLUTCH ENGAGED



III-14Page:

VALVE STATIONCLUTCH ENGAGED/WITH PIN



III-15Page:

VALVE STATIONCLUTCH DECAY

DECAYORIFICE

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FILTER

DOWNSHIFTSOLENOID

TANK

CHARGINGPUMP SCAVENGE

PUMP

ROTARYACTUATOR

SELECTOR VALVEGROUP

ROTARYSELECTOR

SPOOL

PRIORITYREDUCTION

VALVE

LUBERELIEF VALVE

PUMPPRESSURE

DOWNSHIFTPRESSURE

PILOT OILPRESSURE

LUBEPRESSURE

UPSHIFTPRESSURE

TRANSMISSIONCASE

NEUTRALIZERVALVE

RELIEFVALVE

OIL COOLER

UPSHIFTSOLENOID

A

B

D

E

F

G

H

C

PRESSURE CONTROLGROUP

769C - 777C TRANSMISSIONHYDRAULIC SYSTEMTHIRD SPEED FORWARD



III-17Page:

VALVE STATIONPRIMARY PRESSURE

LOAD PISTONPLUG (REMOVED)

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777D SHIFT MODULATION CYCLETHIRD(3&6) TO FOURTH (1&5)

NORMAL SHIFT CYCLE

COMPLETE CLUTCH ENGAGEMENT

INITIAL CLUTCH ENGAGEMENT

NORMAL CLUTCH SLIP

PRIMARYPRESSURE

FILL TIMETIME

418

373353

265

50

0

CLUTCH 5

CLUTCH 1

CLUTCH 3

CLUTCH 6

PRESSURE

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III-19P

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777C SHIFT MODULATION CYCLESECOND TO THIRD

NORMAL SHIFT CYCLE

COMPLETE CLUTCH ENGAGEMENT

INITIAL CLUTCH ENGAGEMENT

NORMAL CLUTCH SLIP

PRIMARYPRESSURE

FILL TIMETIME

418

373

265

80

0

CLUTCH 1

CLUTCH 3

CLUTCH 6

PRESSURE

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COMPLETE CLUTCHENGAGEMENT

INITIAL CLUTCHENGAGEMENT

NORMAL CLUTCHSLIP

HIGH PRIMARY PRESSURE - HARSHSHIFT

LOW PRIMARY PRESSURE - CLUTCHSLIPPING

HIGHPRIMARYPRESSURE

RESTRICTED LOAD PISTONORIFICE

SLOW MODULATION

TIME

NORMALPRIMARYPRESSURE

LOWPRIMARYPRESSURE

SHIFT MODULATIONPROBLEMS

PRESSURE

0

P1

RESTRICTED LOAD PISTONORIFICECLUTCH SLIPPING



III-21Page:

LAB EXERCISES

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 numbernext to the component. During the slide presentation, use this sheet to take notes on the function of eachcomponent.

______ Torque Converter - example: Located on the rear of the engine. Provides a fluid couplingbetween the engine and the transmission and multiplies torque. Contains a lockup clutch formore 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 -

______ Lockup Clutch Solenoid Valve -



III-22Page:

LAB EXERCISESLab 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 numbernext to the component. During the slide presentation, use this sheet to take notes on the function of eachcomponent.

______ Transmission Tank - example: Located on the left side of the truck. Contains a sight gauge forchecking power train hydraulic level.

______ Transmission Pump -

______ Transmission Filter -

______ Transmission Magnetic Suction Screen -

______ Transmission Oil Cooler -

______ Transmission Control Valve -

______ Upshift Solenoid Valve -

______ Downshift Solenoid Valve -



III-23Page:

LAB EXERCISES

TYPICAL OFF-HIGHWAY TRUCKPOWER TRAIN

COMPONENT LOCATIONS

Lab A: Component Location and Identification Worksheet V

Torque Converter and Transmission Hydraulic Systems Component Identification

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LA

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S

TOBRAKE

COOLINGCIRCUIT


7. Inlet Relief Valve

8. Lockup Modulation Valve

9. Scavenge Pump

10. Lockup Solenoid

11. Shuttle Valve

12. Lockup Clutch

Lab B: Torque ConverterHydraulic SystemComponent 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 letteror number of the item in thecorrect blank on theschematic.



III-25Page:

LAB EXERCISES

Lab C: Torque Converter Hydraulic System Testing

Shop Lab Exercise

Procedure:

Perform the following tests listed in the Power Train Testing andAdjusting 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 Nipple1 - 6V4143 Valved Coupler1 - 6V3079 Diagnostic Hose1 - 6V3121 Multitach Group1 - Oil container [approximately 19 l (5 gal.) capacity]1 - Special Instruction "6V3121 Multitach Group" (Form

SEHS7807)



III-26Page:

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 Testing769C - 777C Off-highway Trucks - Worksheet I

Directions: Use this sheet to check off each of the steps listed in the Power Train Testing andAdjusting Service Manual Module.

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III-27P

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LA

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S

Lab D: Tracing Torque Converter Oil System Flow (769D - 777D)

Worksheet I

Directions: Trace the flow of oil during the condition listed below using different colored pencils to show each path.



769D - 777D TORQUECONVERTER

HYDRAULIC SYSTEMTORQUE CONVERTER

DRIVE

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III-28P

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LA

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SLab 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.

TOBRAKE

COOLINGCIRCUIT


769C - 777C TORQUE CONVERTERHYDRAULIC SYSTEM

DIRECT DRIVE



III-29Page:

LAB EXERCISESLab E: Torque Converter Hydraulic System Operation (769D - 777D)

Worksheet I

Directions: 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 shuttlevalve 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 ismaintained by the:

A. inlet relief valve

B. outlet relief valve

C. parking brake release valve

7. Modulation of the lockup clutch is determinedby the:

A. load piston

B. modulation reducing valve

C. load piston orifice

1. The torque converter is in direct drive in thefollowing speeds:

A. REVERSE and FIRST

B. second half of FIRST through SEVENTH

C. NEUTRAL to FIRST

2. If the torque converter lockup solenoid does notreceive an electrical signal in SECOND SPEEDFORWARD, 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 isfrom the:

A. transmission charging pump

B. torque converter charging pump

C. parking brake release pump

4. Excess oil pressure to the torque converterduring a cold start-up is prevented by the_______.

A. inlet relief valve

B. outlet relief valve

C. parking brake release valve

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S

C

A

B

D

E

F

G

H

ON

Lab F: TransmissionHydraulic SystemComponentIdentification(769D - 777D)

Worksheet I

Directions: Write the letter ornumber of the item in thecorrect 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

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LA

B E

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S

VALVE STATION

FROM PUMPTO CLUTCH

Identify Test PortsA. Primary and Clutch Pressures

B. Pilot Pressure

Identify Components1. 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

Lab F:TransmissionHydraulic SystemComponentIdentification

Pressure ControlGroup Valve Station

Worksheet III

Directions: Write theletter or number of theitem in the correctblank on the schematic.



III-32Page:

LAB EXERCISES

Lab G: Transmission Hydraulic System Testing

Shop Lab Exercise

Procedures:

Perform the following tests listed in the Power Train Testing andAdjusting 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 Group1 - 1U5482 Pressure Adaptor Group1 - 3B7282 Nipple1 - 3B6552 Nipple1 - 6V4142 Unvalved Nipple1 - 6V6064 or FT1775 Transmission Test Cover



III-33Page:

LAB EXERCISESLab 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 AdjustingService 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

DUAL STAGE RELIEF LOCKUP CLUTCH DEACTIVATED

SPECS ACTUAL

LOWIDLE

HIGHIDLE

LOWIDLE

HIGHIDLE

PUMP PRESSURE

DUAL STAGE RELIEF LOCKUP CLUTCH ACTIVATED

SPECS ACTUAL

LOWIDLE

HIGHIDLE

LOWIDLE

HIGHIDLE

PUMP PRESSURE

SPECS ACTUAL

LOWIDLE

HIGHIDLE

LOWIDLE

HIGHIDLE

PILOT PRESSURE NO NO

LUBE PRESSURE



III-34Page:

LAB EXERCISES

Lab G: Transmission Hydraulic System Testing769D - 793C Off-highway Trucks - Worksheet II

Directions: Use this sheet to check off each of the steps listed in the Power Train Testing and AdjustingService Manual Module.

CLUTCH CHART

N

R

1

2

3

4

5

6

7

PRIMARY CLUTCH PRESSUREAT LOW IDLE

(LOAD PISTON PLUG REMOVED)STATION CLUTCH SPECS ACTUAL

A

B

C

D

E

F

G

H

PRIMARY CLUTCH PRESSURE AT LOW IDLE(LOAD PISTON PLUG INSTALLED)

SPECS ACTUAL

STATION CLUTCH LOWIDLE

HIGHIDLE

LOWIDLE

HIGHIDLE

A

B

C

D

E

F

G

H



III-35Page:

POSTTEST

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 theselector 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 toremain 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 thatmake the statement incorrect and replace with word(s) to make the statement correct. (Each question isworth 2 points.)

a transmissionExample: 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.

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PO

ST

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ST

VALVE STATION

FROM PUMPTO CLUTCH

Test Ports

Primary Pressure

Pilot Pressure

Clutch Pressure

Components

Load Piston

Pilot Oil Passage

Decay Orifice

Load Piston Plug

Modulation Reduction Valve

Load Piston Orifice

Ball Check Valve

Clutch Pressure Tap

Pilot Oil Plug

Selector Piston

Slug

Pin

Directions: Match thecomponents and test ports withthe associated number or letter.(Each question is worth 1 point.)

13

15 14 10

11

7

9

3128

4

652

1



III-37Page:

POSTTEST

Directions: Use the schematic on page 38. After each statement, circle the correct sequence of eventsthat occurs.

Example: The operator makes a shift from NEUTRAL to FIRST FORWARD.

A. 1-Pilot oil movesselector piston

2-Selector piston closesdrain

3-Load piston movesreducing valve

4-Modulation begins

B. 1-Selector piston closesdrain

2-Pilot oil movesselector piston

3-Modulation begins


A. 1-Rotary selector spoolopens pilot oil passageto drain

2-Load piston oil isdirected throughdecay orifice

3-Selector piston opensdrain

A. 1-Pump oil is directedthrough load pistonorifice

2-Pump oil is directed toclutch

3-Modulation reductionvalve moves

B. 1-Pump oil is directed toclutch

2-Modulation reductionvalve moves

3-Pump oil is directedthrough load pistonorifice

C. 1-Modulation reductionvalve moves

2-Pump oil is directed toclutch

3-Pump oil is directedthrough load pistonorifice

B. 1-Rotary selector spoolopens pilot oil passageto drain

2-Selector piston opensdrain


C. 1-Selector piston opensdrain


3-Rotary selector spoolopens pilot oil passageto drain

C. 1-Modulation begins


3-Selector piston closesdrain

4-Pilot oil movesselector piston



III-38Page:

POSTTESTTorque 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 thatmake the statement incorrect and replace with word(s) to make the statement correct.

a power trainExample: 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

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Test Ports

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

Directions: Match thecomponents and test ports withthe associated number or letter.

2

4

1

7

TO BRAKECOOLINGCIRCUIT5

8D

A

3

6

9

E

C

B

TO BRAKECOOLING CIRCUIT

10

11

769D - 777D TORQUE CONVERTERHYDRAULIC SYSTEM

12



III-40Page:

POSTTESTDirections: Use the schematic on page 41. After each statement, circle the correct sequence of eventsthat occurs.

Example: The operator makes a shift from NEUTRAL to FIRST FORWARD and the ground speed increases.

A. 1-Torque converter is inTC drive

2-Ground speedincreases and thelockup clutchmodulation valve isactivated

3-Lockup clutch engages

B. 1-Lockup clutch engages

2-Ground speedincreases and thelockup clutchmodulation valve isactivated

3-Torque converter is inTC drive

C. 1-Ground speedincreases and thelockup clutchmodulation valve isactivated

2-Lockup clutch engages

3-Torque converter is inTC drive

C. 1-Parking brake releasepump directs oil tolockup reducing valve

2-Pilot oil directed tolockup solenoid valve

3-Parking brake releaseoil directed to lockupmodulation valve spool

A. 1-Parking brake releaseoil directed to lockupmodulation valve spool


3-Parking brake releasepump directs oil tolockup reducing valve

B. 1-Parking brake releaseoil directed to lockupmodulation valve spool

2-Parking brake releasepump directs oil tolockup reducing valve


B. 1-Lockup solenoid valveopens

2-Shuttle valve movesand blocks drain

3-Load piston moves

A. 1-Shuttle valve movesand blocks drain

2-Load piston moves

3-Lockup solenoid valveopens

C. 1-Load piston moves

2-Lockup solenoid valveopens

3-Shuttle valve movesand blocks drain

A. 1-Shuttle valve movesand opens drain

2-Lockup solenoid valvecloses

3-Load piston moves

C. 1-Lockup solenoid valvecloses

2-Shuttle valve movesand opens drain

3-Load piston moves

B. 1-Load piston moves

2-Shuttle valve movesand opens drain

3-Lockup solenoid valvecloses



III-41Page:

POSTTEST

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 ingear

Supplies oil to all clutches

Directs oil to move rotary actuator vane counterclockwise

Maintains and directs oil pressures to the pressure control group

Directions: Match the component to its primary function.



III-42Page:

POSTTEST

Directions: Modified True/False. If a statement is false, underline or circle the word or words thatmake the statement incorrect and replace with word(s) to make the statement correct.

a transmissionExample: 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.

CH

AP

TE

R : P

ow

er Train

777D O

ff Hig

hw

ay Truck

III-43P

age:

PO

ST

TE

ST

Test Ports

Pump Pressure

Upshift Pressure

Downshift Pressure

Pilot Pressure

Lube Pressure

Components

Scavenge Pump

Priority 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

Directions: Match thecomponents and test ports withthe associated number or letter.

C

8

13

9 4

1

1410

11

3

12

6

5

7

A

B

D

E

F

G

H

B

A

E

C

D

ON

2

15 16

769D- 777D TRANSMISSIONHYDRAULIC SYSTEM



III-44Page:

Directions: Use the schematic on page 45. After each statement, circle the correct sequence of eventsthat occurs.

Example: The operator has moved the shift lever from NEUTRAL to FIRST FORWARD.

A. 1-Downshift solenoid isde-energized

2-Upshift solenoid isenergized

3-Rotary actuator movesto FIRST SPEEDFORWARD

B. 1-Rotary actuator movesto FIRST SPEEDFORWARD

2-Downshift solenoid isde-energized


C. 1-Upshift solenoid isenergized

2-Rotary actuator movesto FIRST SPEEDFORWARD

3-Downshift solenoid isde-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 valvemoves

2-Pilot oil flows throughrotary selector spool toone station

3-Downshift solenoid isenergized

B. 1-Pilot oil flows throughrotary selector spool toone station

2-Downshift solenoid isenergized

3-Neutralizer valvemoves

C. 1-Downshift solenoid isenergized

2-Neutralizer valvemoves

3-Pilot oil flows throughrotary selector spool toone station

A. 1-Charge pump oil flowsto priority reductionvalve

2-Pilot oil flows toneutralizer valve

3-Rotary selector spoolblocks charge pump oilto neutralizer valve

C. 1-Pilot oil flows toneutralizer valve

2-Rotary selector spoolblocks charge pump oilto neutralizer valve

3-Charge pump oil flowsto priority reductionvalve

B. 1-Rotary selector spoolblocks charge pump oilto neutralizer valve

2-Pilot oil flows toneutralizer valve

3-Charge pump oil flowsto priority reductionvalve

A. 1-Charge pump movesthe upshift valve


3-Rotary actuator oilmoves the downshiftvalve

B. 1-Upshift solenoid isenergized

2-Charge pump oilmoves the rotaryactuator

3-Rotary actuator movesthe rotary selectorspool

C. 1-Rotary actuator oilmoves the downshiftvalve


3-Charge pump movesthe upshift valve



III-45Page:

Directions: After each statement, circle T if the statement is TRUE, and F if the statement is FALSE.

Example: When activated, the shift solenoids allow oil to flow to the T Frotary actuator.

1. On some ICM transmissions, the Dual Stage Relief Valve is activated T Fduring torque converter lockup.

2. On all ICM transmission controls, REVERSE is an upshift from T FNEUTRAL 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 Fthe rotary selector spool provides a path to drain for two clutches.

4. On all ICM transmission controls, the priority reduction valve controls T Fthe pressure of the "pilot oil" that is used to shift the selector pistonin each station.

5. The load piston orifice in an ICM transmission is a "cascade-type" and T Fcontrols the modulation of clutch engagement.

6. In an ICM transmission, the "primary pressure setting" in each station T Fcan 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 Fis low, the load piston springs should be replaced.

10. When manually rotating the rotary selector spool with the engine T Frunning, power to the shift solenoids must be disconnected.

Service TrainingMALAGA

777D Off Highway TruckStudent book

AdolfoAugust 1997

SYSTEMS

03PTRAIN

Documents

service training

brake cooling

tage relief

frotary selector

priority reduction

pressure control

rotary selector

lube relief