Section 25

Chapter 2

6-12780NH

DIFFERENTIAL LOCK CONTROL SYSTEM

How It Works

SECTION 25 - HYDRAULIC PUMP DRIVE - CHAPTER 2

25-2

TABLE OF CONTENTS

DIFFERENTIAL LOCK ....................................................................................................................................... 25-3General Description ........................................................................................................................................ 25-3

ELECTRONIC DIFFERENTIAL LOCK CONTROL ............................................................................................ 25-5General Description ........................................................................................................................................ 25-5Operational Modes .......................................................................................................................................... 25-5

DIFFERENTIAL LOCK CONTROL MODES ...................................................................................................... 25-7

DIFFERENTIAL LOCK CONTROL ..................................................................................................................... 25-8

DIFFERENTIAL LOCK FUNCTIONAL TESTS ................................................................................................... 25-9Differential Lock Valve .................................................................................................................................. 25-10Solenoid Cartridge Valve .............................................................................................................................. 25-10Differential Lock Clutch Disengaged ............................................................................................................. 25-11

TROUBLESHOOTING ..................................................................................................................................... 25-12Problem – Differential lock will not engage ................................................................................................... 25-12Differential Lock Engaged ............................................................................................................................. 25-13Problem – Differential lock will not disengage .............................................................................................. 25-14

PTO/DIFFERENTIAL LOCK VALVE CIRCUIT ................................................................................................. 25-15

DIFF LOCK CONTROL SYSTEM .................................................................................................................... 25-17

SECTION 25 - HYDRAULIC PUMP DRIVE - CHAPTER 2

25-3

DIFFERENTIAL LOCK

General Description

The Differential Lock consists of the differential lock piston, differential lock control valve, differential lock controlswitch, brake pedal switches, true ground speed circuit, hitch position circuit, transmission speed circuit, andelectronic control modules (through the Data Bus). Because the differential lock is electronically controlledautomatic operation is possible.

The PTO/Differential Lock valve is mounted externally on top of the rear frame transmission housing. The controlvalve is supplied with regulated circuit pressure from the priority/regulator valve. This pressurized supply is directedto the differential lock piston for engagement. If the differential lock is activated, pressurized oil from the regulatedsupply circuit is ported to the differential lock piston in the differential carrier housing. As the piston extends frictiondiscs and separator plates are locked together. The separator plates are pinned to the differential carrier, while thefriction plates are splined to the left differential side gear. When the differential lock is applied, the clutch pack lockscausing the left side gear to rotate with the differential carrier. This eliminates all differential action, causing powerto be transmitted equally through both rear axles.

The PTO controller supplies current to the differential lock valve to activate the clutch based on commands from theoperator (Differential Lock switch) and signals supplied to it from the brake pedal switches, true ground speedcircuit, hitch position control system, and transmission speed signal circuit.

Diagnosing control system faults is accomplished by reading appropriate faults codes through the instrumentcluster display or the service tool. Refer to PTO system fault code section of this manual for a complete list of faultcodes related to the PTO, MFD, and Differential Lock system.

SECTION 25 - HYDRAULIC PUMP DRIVE - CHAPTER 2

25-4

RI02E0861. PTO/DIFF LOCK VALVE 2. DIFF LOCK CLUTCH SOLENOID

1

2

SECTION 25 - HYDRAULIC PUMP DRIVE - CHAPTER 2

25-5

ELECTRONIC DIFFERENTIAL LOCK CONTROL

General Description

The Differential Lock consists of the differential lockclutch, differential lock control valve, differential lockcontrol switch, brake pedal switches, true groundspeed circuit, hitch position circuit, transmissionspeed circuit, and electronic control modules(through the Data Bus). Because the differential lockis electronically controlled, automatic operation ispossible.

All differential lock operator commands are sent tothe Arm Rest Control Module then relayed to thePTO controller via the Data Bus. Transmission speedand true ground speed signals are sent to theinstrument Cluster Unit (ICU) then relayed to thePTO control ler. Diagnost ic and programminginformation are communicated between the PTOcontroller and the Instrument Control Unit (ICU) byway of the Data Bus.

Operational Modes

The differential lock system operates in one of two (2)modes based on operator commands and the signalsreceived from the other tractor systems.

RH02F017

OFF (see NOTE below)ON (Differential Symbol)Automatic Differential Lock Control (A)

NOTE: It is not possible to disengage the differential lock with the switch control. Pushing either brake pedal willdeactivate the differential lock.

SECTION 25 - HYDRAULIC PUMP DRIVE - CHAPTER 2

25-6

RH02G333

1. DIFFERENTIAL LOCK SWITCH

1

SECTION 25 - HYDRAULIC PUMP DRIVE - CHAPTER 2

25-7

DIFFERENTIAL LOCK CONTROL MODES

ON (Differential Symbol) – When the differential lock switch is placed in the ON position the differential lock will be activated. A differential symbol will be illuminated on the tractor monitor.The differential lock will disengage when either brake pedal is pushed.

NOTE: It is not possible to disengage the differential lock with the switch control. Pushingeither brake pedal will deactivate the differential lock.

The differential lock switch has three (3) positions. The mid switch position is OFF when the differential lock is deactivated. The same switch position is ON when the differential lock is activated manually.

Automatic Differential Lock Control – When the differential lock switch is placed in theAutomatic position (A symbol) the differential lock will be activated (differential symbol will beilluminated on the tractor monitor) unless the following conditions are applicable.

1. Operating with the hitch position control lever down and the hitch is raised with the UP/DOWN switch (End ofRow Feature deactivates differential lock).

2. One of the brake pedals is depressed and slip is below 15%.

3. Ground speed is in excess of 10 MPH and slip is below 15%.

NOTE: If the differential lock automatically disengages when ground speed exceeds 10 MPH. The differential lockwill not automatically engage when ground speed decreases. To reactivate the differential lock after speeddecreases (below 8 MPH), place the switch in the AUTO position and return the switch to the middle position.

RH02F017

RH02F017

SECTION 25 - HYDRAULIC PUMP DRIVE - CHAPTER 2

25-8

DIFFERENTIAL LOCK CONTROL

RI98G146

INST.CONTROLMODULE

DATA

BUS

KEYSWITCH

OFF/ON OFF/ON

OFF

ON

ARMRESTCONTROLMODULE

ENGINE

TRANSMISSION

PTOCONTROL

CANTRANSCEIVER

MICROCONTROLLER

MFD/DIFF LOCKCONTROL

LH BRAKEPEDALSWITCH

RH BRAKEPEDALSWITCH

CLEAN GROUND

IMPLEMENTBRAKELIGHTS

TRACTORBRAKELIGHTS

BRAKELIGHTRELAY

RANGE TRANSMISSION HOUSING

MFDVALVE

MFDCLUTCH

REAR FRAME HOUSING

DIFF LOCKVALVE

DIFF LOCKCLUTCH

PTO CONTROL MODULE

TRUE GROUNDSPEED SENSOR

TRANSMISSIONSPEED SENSOR

DIFF. LSWITCH

MFDSWITCH

PTOSWITCH

SECTION 25 - HYDRAULIC PUMP DRIVE - CHAPTER 2

25-9

DIFFERENTIAL LOCK FUNCTIONAL TESTS

IMPORTANT: Hitch position and wheel slip willinfluence differential lock operation when tractor is inmotion.

IMPORTANT: Hitch position and wheel slip willinfluence differential lock operation when tractor is inmotion.

Switch Position Engaged/Disengaged

Operational Comments

ON Engaged The differential Lock icon will illuminate.

I f one (or both) brake pedals is pushed thedifferential lock light will go out and the differentiallock will be deactivated.

AUTO Disengaged As hitch raises and reaches upper 30% of travel.(lever down/switch.

NOTE: If slippage is above 15% the differential lockwill engage (or stay engaged).

Disengaged As travel speed exceeds 10 MPH.

NOTE: If slippage is above 15% the differential lockwill engage (or stay engaged).

Disengaged As one or both brakes is applied. Differential lock willre-engage if both brake pedals are released.

Engaged As hitch lowers below upper 30% of travel. (leverdown/switch down)

Engaged Brakes not applied.

RH02F017

RH02F017

SECTION 25 - HYDRAULIC PUMP DRIVE - CHAPTER 2

25-10

RI02E087

Differential Lock Valve

The differential lock valve is a closed center valve and is contained as a part of the PTO valve. Oil is supplied to thedifferential lock cartridge valve from the regulated pressure circuit. The differential lock clutch supply flow isdistributed internally (no external tubing) to the clutch. The valve is mounted on the top of the rear frametransmission housing. The following components of the PTO valve are involved in the differential lock system.

Solenoid Cartridge Valve

The solenoid is controlled by an armrest mounted rocker switch. The armrest controller communicates (via theData Bus) with the PTO controller. The PTO controller supplies current to the differential lock valve to activate thedifferential lock clutch based on commands from the operator (differential lock switch) and signals supplied to itfrom the brake pedal switches, true ground speed circuit, hitch position control system, and transmission speedsignal circuit. The differential lock is a hydraulically applied clutch.

1. PTO/DIFF LOCK VALVE 2. DIFF LOCK SOLENOID

1

2

SECTION 25 - HYDRAULIC PUMP DRIVE - CHAPTER 2

25-11

Differential Lock Clutch Disengaged

When the switch is in the disengaged position (middle) and a brake pedal is pushed, the solenoid will be de-energized. Regulated pressure will be at the valve cartridge. The piston of the differential lock clutch ismechanically returned to the neutral position. As the piston retracts, oil will be ported to the transmission housingand the differential lock clutch will disengage

NOTE: It is not possible to disengage the differential lock with the switch control. Pushing either brake pedal willdeactivate the differential lock.

The differential lock switch has three (3) positions. The mid switch position is OFF when the differential lock isdeactivated. The same switch position is ON when the differential lock is activated manually.

RT98A024

1

2

3

4

1. PTO SOLENOID 3. TO DIFF LOCK CLUTCH (PORTED THROUGH BACK OF VALVE)

2. REGULATED SUPPLY PASSAGE (THROUGH TOP OF VALVE BODY)

4. DIFF LOCK SOLENOID

SECTION 25 - HYDRAULIC PUMP DRIVE - CHAPTER 2

25-12

TROUBLESHOOTING

Problem – Differential lock will not engage

1. Check for PTO System fault codes.A. If fault codes are found, follow procedures outlined in PTO system fault code troubleshooting in this

section.

2. Push either brake pedal switch to deactivate the differential lock. Check the tractor monitor for the differentiallock icon in the instrumentation display.

A. If the differential lock icon is not displayed, this is an indication the electrical control circuit is functioningcorrectly. Go to step 4.

B. If the differential lock icon is displayed, this in an indication the electrical control circuit is not functioningcorrectly. Check fault codes, controller, and data bus function.

3. Activate the differential lock with the manual switch position. Check for 12 VDC at differential lock valve coil.A. If 12 VDC is available to the coil, the differential lock electrical circuit is functioning properly.

B. If 12 VDC is not found, troubleshoot the differential lock electrical circuit.

1. Check wires 530A (R) and 175E (BK) ground.

2. Check all connections for excessive resistance.

Apply the brakes, this will deactivate the differential lock. Check for 12 VDC at differential lock valve coil.

C. If 12 VDC is available to the coil, the differential lock electrical circuit is not functioning properly.

1. Check left and right brake switches.

D. If 12 VDC is not found the differential lock electrical circuit is functioning properly.

4. Turn the ignition switch to the OFF position. Be prepared to press and hold the PROG key on the TractorMonitor within the first 10 seconds after restarting the engine.

- Start and run the engine at low idle. Press and hold the PROG key

- The tractor monitor will emit a short beep and display INST SET MENU. Press the DECR key until the displayreads TRANS SET MENU.

- Next press the PROG key until the display reads TRANS VIEW. Continue to press the PROG key until the displayreads “PresS”.

- The powershift system manifold pressure (in KPa) is now visible on the bottom of the display.

NOTE: Start the engine and heat the transmission oil to 120°F (49°C).

5. While viewing the display, activate the Differential Lock. The display pressure should dip, then recover tonormal regulated pressure. If the pressure dips, but does not recover there is a leak in the Differential Lockcircuit. Repeat this check several times.

6.A. Inspect the differential lock valve cartridge for leaking seals.

B. Inspect the differential lock slip ring teflon seals.

C. Inspect the differential lock piston o-ring.

7. Check and repair the differential lock clutch as needed.

SECTION 25 - HYDRAULIC PUMP DRIVE - CHAPTER 2

25-13

Differential Lock Engaged

When the switch is in the engaged position (differential symbol) the solenoid will be activated. Oil pressure,available to the valve cartridge, will be ported (internally) to the rear frame transmission housing of the tractor. Theclutch will be engaged, as the piston extends, locking the friction and separator plates together. The clutch packlocks causing the left side gear to rotate with the differential carrier, eliminating differential action.

RH98H056

DIFFERENTIAL LOCKCLUTCH ASSEMBLY

SECTION 25 - HYDRAULIC PUMP DRIVE - CHAPTER 2

25-14

TROUBLESHOOTING

Problem – Differential lock will not disengage

1. Check for PTO fault codes.A. If fault codes are found, follow procedures outlined in PTO system fault code troubleshooting in this

section.

2. Place the differential lock switch in the ON position. Check the tractor monitor for the differential lock icon in theinstrumentation display.

A. If the differential lock icon is displayed, this is an indication the electrical control circuit is functioningcorrectly. Go to step 4.

B. If the differential lock icon is not displayed, this in an indication the electrical control circuit is notfunctioning correctly. Check fault codes, controller, and data bus function.

3. Place the differential lock switch in the ON position. Check for 12 VDC at differential lock valve coil.A. If 12 VDC is available to the coil, the differential lock electrical circuit is functioning properly.

B. If 12 VDC is not found, troubleshoot the differential lock electrical circuit.

1. Check wires 530A (R) and 175E(BK) ground.

2. Check all connections for excessive resistance.

Apply the brakes, this will deactivate the differential lock. Check for 12 VDC at differential lock valve coil.

C. If 12 VDC is available to the coil, the differential lock electrical circuit is not functioning properly.

1. Check left and right brake switches.

D. If 12 VDC is not found the differential lock electrical circuit is functioning properly.

4. Check and repair the differential lock clutch as needed.

SECTION 25 - HYDRAULIC PUMP DRIVE - CHAPTER 2

25-15

PTO/DIFFERENTIAL LOCK VALVE CIRCUIT

RH02A059

NOTE: Refer to Differential Lock electrical schematic diagram.

BEVELPINLUBE

DIFF LOCKSOLENOID

REGULATEDSUPPLY

PTOCLUTCHLUBE

DIFFERENTIALLOCK PISTON

PTO CLUTCHPISTON

PTOSOLENOID

SECTION 25 - HYDRAULIC PUMP DRIVE - CHAPTER 2

25-16

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25-17

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SECTION 25 - HYDRAULIC PUMP DRIVE - CHAPTER 2

PT

O C

ON

TR

OLL

ER

GR

AY

J1

ENGINE RPM

RIGHT BRAKE

LEFT BRAKE

OPEN

PTO "ON"

OPEN

CDB HI (TR)

CDB LO (TR)

OPEN

PTO SPEED SHAFT

OPEN

PTO SPEED SIGNAL

BLA

CK

J2

SWITCHED B+

OPEN

BRAKE LIGHT RELAY

PTO SOLENOID B+

PTO SOLENOID RETURN

OPEN

OPEN

OPEN

DIFF SOLENOID B+

MFD SOLENOID B+

OPEN

CLEAN GROUND

CLEAN GROUND

CHASSIS GROUNDCHASSIS GROUND

CLEAN GROUND

UNSWITCHED POWER

SWITCHED POWER

UNSWITCHED POWER

SWITCHED POWER

PTO CONTROLLER SYSTEM

MFD SOLENOID

DIFFERENTIAL SOLENOID

PTO SOLENOID

LEFT BRAKE

SWITCH (NC)

RIGHT BRAKE

SWITCH (NC)

PTO SHAFT

SPEED

SENSOR

PTO DUAL

SPEED

SENSOR

PTO CONTROLLER SYSTEM

SECTION 45SECTION 44

J5

1

2

3

4

5

6

56M

9

10

11

12

56M

1

2

3

4

5

6

7

8

9

10

11

12

57M

B

A

145M

A

B

145F

C

B

A

146M

A

B

C

146F

B

A

336M

A

B

336F

A11

SECTION 71 2 SHT

CONN 278M, CAV L

TO AFS AT

SECTION 54 2 SHT

TO CONN 335M, CAV 1

SECTION 38 2 SHT

TO SPLICE T3

SHT 2 SECTION 57

AT RING TERM 200F

TO CLEAN GND

2

1

160M

2

1

158M

B

A

159M

SECTION 52 2SHT

FUSE BLOCK 262, CAV C8

JUMPER TO FUSE #39

B

A

163M

A

B

163FC8

SECTION 341SHT

AT CONN 263F, CAV F1

LIGHT RELAY

TO BRAKE

10

11

15

14

29

10F

29

14

15

11

10

10M

SECTION 492SHT

CAVITY 7

AT CONN 137M

CONTROLLER

TO ARMREST

B

A

162M

A

B

162F

SECTION 38 2SHT

AT SPLICE T3

TO CLEAN GROUND

SECTION 38 2SHT

AT SPLICE T3

TO CLEAN GROUND

0.8-R

530A

0.8-R

540A

1.0-Bk

175E

1.0-Bk

175D

SECTION 211SHT

AT SPLICE C9

TO SWITCHED B+

0.8-LU597A

0.8-Bk

598A

10A

FUSE #38

1.0-R

599E 3.0-R

200C

0.8-R

599D

0.8-R

599C

0.8-R

311A

1.0-R

599B

0.8-K

510B

0.8-K

509B

SECTION 321 SHT

AT SPLICE A13

TO CHASSIS GROUND

SECTION 251 SHT

TO SPLICE F6

0.8-Bk

174E

0.8-Bk

174C 0.8-Bk

174D

0.8-W

294B

0.8-W

294A

0.8-Y

295A

0.8-Y

293A

0.8-K

509A

0.8-K

510A

0.8-Y

216D

SECTION 321 SHT

AT SPLICE A13

TO CHASSIS GROUND

0.8-T

702A

1.0-R

599A

0.8-LU

597A

0.8-R

540A

0.8-R

530A

0.8-Bk

598A

1.0-Bk

179F

SECTION 54 2SHT

TO CONN 335M, CAV 3

1.0-Bk

179BJ

0.8-Bk

179G

0.8-Bk

179H

3.0-Bk

179C

0.8

-Y

293B

3.0

-B

k17

9A