Land Rover Defender: Description

TRANSFER CASE EXPLODED VIEW

1. Synchronization spring (quantity 3)
2. Spring bracket
3. Multiplate clutch ( 10 friction plates, 10 steel plates)
4. Synchronization cup
5. Drum clutch
6. Plate clutch pack
7. Synchronization spring
8. Differential assembly
9. Shifting sleeve
10. Screw (quantity 6)
11. Synchronizer
12. Bearing
13. Rear housing
14. Transfer case output seal
15. O-ring seal
16. Bearing needle
17. Rear output flange
18. Bearing needle
19. TCCM
20. Bolt (quantity 2)
21. O-ring
22. O-ring
23. TCCM seal
24. Retaining ring
25. Retaining ring
26. Transfer case motor shaft bearing
27. Transfer case motor shaft
28. Bolt (quantity 2)
29. High/low range position sensor
30. Filler Plug
31. Shim
32. Shifting fork - High/Low range
33. Circlip
34. Transfer case actuator shaft
35. Clutch control disc
36. Gear
37. Actuator shaft bearing
38. Circlip
39. Actuator shaft bearing bracket
40. Bolt (quantity 2)
41. Shim
42. Drain plug
43. Transfer case housing bearing
44. Bearing
45. Circlip
46. Retaining ring
47. Retaining ring
48. Bearing needle
49. Clutch lever
50. Ball (quantity 5)
51. Fixed lever
52. Bearing needle
53. Reluctor ring
54. Drive chain sprocket
55. Drive chain sprocket
56. Drive chain
57. Needle roller bearing
58. Retaining ring
59. Oil pump - Spacer ring
60. Oil pump
61. O-ring seal
62. Bearing retaining ring
63. Shim
64. Circlip
65. Front housing
66. Adapter vent Screw (quantity 2)
67. Dowel pin (quantity 2)
68. Chain guide (quantity 2)
69. Bolt (quantity 19)
70. O-ring
71. Input shaft plug
72. Input shaft
73. Needle roller bearing
74. Circlip
75. Front output flange bearing
76. Front output flange seal
77. Front output flange seal ring
78. Front output flange

TRANSFER CASE - SECTIONAL VIEW

1. Input shaft
2. Front housing assembly
3. Clutch lever
4. Planetary gear set
5. Rear output flange
6. Center differential assembly
7. Multiplate clutch
8. Actuation shaft
9. Rear housing assembly
10. Front output sprocket
11. Chain drive
12. Front output flange
13. Drive sprocket
14. Oil pump assembly

TRANSFER CASE POWER FLOW

Output torque from the transmission is transferred to the input shaft of the transfer case. The input shaft of the transfer case transfers the torque onto the planetary sun gear and planetary pinion gears. The planetary pinion gears are held in place by the planetary pinion shafts, which are connected to the differential carrier, drive the differential pinion gears. The torque is then distributed to both the front and rear differential side gear, which are connected to the outputs of the transfer case. The rear differential side gear is connected directly to the rear output flange. The front differential side gear is connected to the chain drive and therefore to the front output sprocket, which provides front output flange rotation.

Front casing assembly

The front casing assembly provides the location for the input shaft bearing, the front output flange bearing and the oil pump. The front casing assembly is equipped with threaded holes to install the chassis mounting bush. The front casing assembly also has 2 lifting eyes and 1 breather cartridge for the transfer case breather pipe. The breather pipe allows equalization between atmospheric and internal transfer case pressure.

The front casing has 2 snubbers, 1 on drive side of the chain and 1 on the coast side, which are secured with 2 screws. The snubbers are suppressing chain vibrations which can occur under medium acceleration conditions, therefore improving Noise, Vibration and Harshness (NVH) issues. During normal operation the drive chain does not contact the snubbers.

Oil pump

An oil pump assembly is located in the front casing to provide lubrication for the bearings and rotary components through cross-drillings in the input shaft. A flat-sectioned coupling on the input shaft drives the rotor of the pump, the stator is installed to the front housing assembly. A tube is attached to the pump, which leads into a calm suction area at the bottom of the 2 casing assemblies. The collector magnet in the suction area of the pump collects any metallic debris.

Rear casing assembly

The rear casing assembly provides the location for the rear output flange bearing, the transfer case motor and the oil filler and drain plug. Fins are cast into the rear casing assembly to improve heat dissipation. The part number and serial number are printed on a bar code label, which is bonded to the rear casing assembly.

Chain drive

The chain-drive transfers drive from the center differential to the front output flange. The drive chain connects the drive chain sprocket on the transfer case input shaft with the drive chain sprocket on the front output flange. As both sprockets have the same number of teeth, the rotational speed of both sprockets is identical.

Center differential

1. Drum clutch
2. Plate clutch pack
3. Synchronization cup
4. Synchronization spring
5. Differential carrier
6. Planetary pinion gear shaft (quantity 3)
7. Planetary pinion gear (quantity 3)
8. Pinion gear shaft (quantity 3)
9. Pinion gear (quantity 3)
10. Shifting sleeve
11. Multiplate clutch basket
12. Bolts (quantity 6)
13. Synchronizer sleeve
14. Planetary sun gear
15. Differential side gear (quantity 2)

The center differential assembly is the primary feature of the twin speed transfer case. Torque is transmitted through the center differential carrier and distributed to the differential gears and the front and rear output flanges. The planetary gear set, for the high/low range change function, is also an integral part of the center differential assembly.

The assembly comprises 3 differential pinion gears and shafts, which are equally spaced within the center differential carrier. The differential shafts have a rigid connection to the differential carrier. The 3 planetary pinion gears and shafts are located between the pinion gears. The planetary sun gear and 2 differential side gears are located in the centerline of the differential carrier.

The planetary ring gear is supported in both directions by the differential casing and the differential cover. The planetary ring gear is connected to a shifting sleeve, which is engaged in either high or low range.

The multiplate clutch basket, which is welded to the differential casing, supports the friction plates. The dogteeth, synchronization cup and synchronization spring supports high range engagement for the range change function.

1. High range position
2. Low range position

1. Dogteeth
2. Planetary pinion gears
3. Planetary ring gear
4. Shifting sleeve
5. Low range dogteeth
6. Rear carrier assembly

When high range is engaged, the shifting sleeve connects to the differential carrier through dogteeth. The planetary ring gear, through the shifting sleeve, and the planetary pinion gears, through the planetary shafts are also attached to the differential carrier. The planetary gear set rotates as 1 unit and therefore turns the differential side gear with a 1 : 1 ratio.

In low range, the motor moves the shifting sleeve in the direction of the low range dogteeth. The low range dogteeth is installed to the rear carrier assembly. The shifting sleeve is engaged with the low range dogteeth. The planetary ring gear, through the shifting sleeve, is stationary. The planetary pinion gears, through the planetary bolts, turn the differential side gears with 2.93 : 1 ratio.

Multiplate clutch assembly

1. Drive chain sprocket
2. Ball ramp mechanism
3. Clutch plates
4. Cup springs
5. Clutch piston
6. Clutch lever

The aim of the multiplate clutch assembly is to prevent excessive differential slip and therefore maximize the traction performance of the vehicle. The function is fundamentally different from the 'braked' traction control, which can only counteract differential slip when it occurs.

A certain amount of differential slip is required to allow the vehicle to turn corners. A certain amount of differential slip is also required to allow the vehicle to remain stable under control of the Anti-Lock Brake System Control Module (ABS). The TCCM monitors the drivers demands through the primary vehicle controls and automatically sets the slip torque at the differential. The system is completely automatic and does not require any special driver input.

The multiplate clutch assembly actively controls the torque flow through the center differential and optimizes the torque distribution in the driveline. The multiplate clutch assembly biases the torque from the transmission to the front differential or rear differential and wheels with the higher grip. The torque biasing prevents the wheels with the lower grip from spinning.

The multiplate clutch assembly comprises:

• A drive chain sprocket, which is connected to the front differential side gear.
• Clutch levers with the ball ramp mechanism.
• Clutch hub as support for the clutch plates.
• Clutch piston to generate friction between the clutch plates.
• Pack of cup springs to return the clutch piston into its original position.

The 1 set of friction plates are connected to the clutch hub, the other set of friction plates are connected to the multiplate clutch basket. The multiplate clutch basket is welded to the center differential housing.

Multiplate clutch actuation

1. Shifting fork - High/Low range
2. Fixed lever
3. Clutch lever
4. Clutch control disc
5. Transfer case motor shaft
6. Gear
7. Actuation shaft

Transfer case motor position for clutch control mode

1. Shifting fork - High/Low range
2. Fixed lever
3. Clutch lever
4. Clutch control disc
5. Motor shaft
6. Gear
7. Actuation shaft

During range change operation, when the multiplate clutch is open, the center differential cannot be locked and the torque cannot be biased. When the range change is complete the system returns to clutch control mode.

High range actuation sequence

1. Shifting fork - High/Low range
2. TCCM
3. Gear
4. Actuation shaft

The rotational movement of the actuation shaft moves the shifting fork - High/Low range to the high range position.

The shifting fork - High/Low range then moves the shifting sleeve into the high range position. After the synchronization sequence, the planetary ring gear is connected to the high range dogteeth, through the shifting sleeve, on the differential carrier. In this position the input speed equals the output speed, which equates to a high range ratio of 1 : 1.

Low range actuation sequence

1. Shifting fork - High/Low range
2. TCCM
3. Gear
4. Actuation shaft

The rotational movement of the actuation shaft moves the shifting fork - High/Low range to low range position. The shifting fork - High/Low range then moves the shifting sleeve into the low range position. The planetary ring gear is then connected to the low range dogteeth, through the shifting sleeve, on the rear carrier assembly. The output speed is then reduced by a ratio of 2.93 : 1.

NOTE: During the range change process there is no clutch lever actuation and therefore torque biasing is not available during the range change process.

Transfer Case Control Module with integrated actuator

1. Twin speed transfer case
2. TCCM

The TCCM comprises an integrated control module and a brushless Direct Current (DC) motor. The TCCM is installed to the twin speed transfer case. The integrated transfer case motor is controlled by the TCCM to operate both the high /low range change and the torque-biasing device (multiplate clutch).

The TCCM detects wheel slip and other vehicle conditions through various inputs from other control modules. The TCCM controls the multiplate clutch based on these inputs to provide optimal torque distribution to the front differential and rear differential. The TCCM also receives range change requests from the range change selection switch and controls high/low gear change. The multiple clutch control and range change actuation are achieved by the integrated transfer case motor through a worm gear which drives an actuation shaft. The TCCM monitors the rotational position of the integrated transfer case motor by a hall effect sensor installed within TCCM.

The actuation shaft rotational movement is monitored by a high/low range position sensor installed in the transfer case. The electrical power and ground to the high/low range position sensor is provided by TCCM. The high/low range position sensor sends a Pulse Width Modulation (PWM) signal to the TCCM through hardwired connection.

The TCCM is connected to the FlexRay and controls transfer case operation. The TCCM receives a power supply through a relay from:

• A 30A fuse link located in the Engine Junction Box (EJB).
• The power supply relay is controlled by the relay - extended ignition which is controlled by Body Control Module (BCM)/ Gateway Control Module (GWM).

When the TCCM is replaced, the JLR approved diagnostic system must be connected to the vehicle and the "New Module Replacement" procedure must be completed.

Range status indication

The range change selection switch has a Light Emitting Diode (LED), this LED operates in 3 ways:

• The LED illuminates when the twin speed transfer case is in low range.
• The LED is switched OFF when the twin speed transfer case is in high range.
• The LED is flashing when range change operation is in progress.

There is a message displayed in the Instrument Panel Cluster (IPC) message center. The message can also inform the driver of any faults with the twin speed transfer case.

The low range status warning indicator in the IPC has the following logic:

• The warning indicator illuminates when the twin speed transfer case is in low range.
• The warning indicator is switched OFF when the twin speed transfer case is in high range.
• The warning indicator is flashing when range change is pending or range change is in progress.

The following table shows the messages that can be displayed in the message center relating to the transfer case:

Transfer Case Control Module inputs/outputs

• Power supply through a relay controlled by the BCM/ GWM.
• Ground.
• High/Low range position sensor ground.

The TCCM receives the following inputs:

• High/Low range position sensor signal
• FlexRay messages.

The TCCM sends the following outputs:

• High/Low range position signal power supply
• FlexRay messages.

Range change selection switch

1. Integrated Control Panel (FCIM)
2. Range change selection switch

The range change selection switch is a momentary switch and located in the FCIM.

When the range change selection switch is operated, the FCIM sends a message to the Heating, ventilation, and air conditioning (HVAC) control module. The message is sent on the private Controller Area Network (CAN) bus. The HVAC control module transmits this message to the BCM/ GWM. The BCM/ GWM transmits this message to the FCIM through the FlaxRay.

A single press of the range change selection switch initiates range change when all the required conditions for range change are met. The range change request is delayed for 1 minute when the vehicle speed or the TCS position are out of operating condition. When the request is delayed, a corresponding warning message is displayed in the IPC message center.

When all the required conditions are met a single press of the range change selection switch initiates range change in the twin speed transfer case.

The range change selection request is delayed for 1 minute when:

• The vehicle speed for range change is above 60 km/h (37 mph).
• The TCS not in the requested position.

While the request is delayed, driver can cancel the request by pressing the range change selection switch.

When the vehicle speed condition or the TCS position condition is not in the requested operating range within 1 minute, the range change request is canceled.

Range change is available only when engine is running.

High/Low range change Light Emitting Diode

The high/low range change LED is connected to the FCIM. The TCCM sends the range change status by a FlexRay to the BCM/ GWM. The BCM/ GWM transmits this signal to the HVAC control module. The HVAC control module transmits this signal through private CAN bus to the FCIM. The FCIM illuminates the high/low range change LED depending on the range change status from the TCCM.

When the transfer case is in high range, the switch LED is not illuminated.

While range change is in progress, the LED flashes ON until the new range status has been achieved.

High/Low range position sensor

1. Twin speed transfer case
2. High/Low range position sensor

The high/low range position sensor detects the rotational angle of the actuation shaft. The actuation shaft angle position is correlated to the high/low fork shift position and the clutch torque control position. The high/low range position sensor output controls the actuation shaft position with a PWM signal to the TCCM. The high/low range position sensor output controls the actuation shaft when the transfer case is in high or low range, or during range change. The high/low range position sensor output also controls the clutch torque control position while the system is in high or low range.

The TCCM check the actuation shaft position when the TCCM wakes up and engine starts. The high/low range position sensor is connected to the TCCM through a 3-pin connector.

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