Part 2

Transmission Description

Power Flow - Reverse Gear





X = Operating





X = Operating
The planetary gear trains are in the following conditions:
- Front planetary gear train
- Input: Ring gear
- Locked: Sun gear
- Output: Carrier
- Rear planetary gear train
- Input: Middle sun gear
- Locked: Carrier
- Output: Ring gear
Front Planetary Gear Train
The input shaft rotates in a clockwise direction, driven by the torque converter. The planetary ring gear rotates clockwise with the input shaft.
The pinion gear rotates clockwise on its axis and orbit. The planetary sun gear is locked by the fluid pump which causes it to press against the planetary ring gear and orbit the sun gear, rotating on its axis. The planetary carrier rotates clockwise with the pinion gear orbit.
Clutch (C3) is activated and rotates clockwise and locks the planetary carrier to the rear planetary middle sun gear.
Rear Planetary Gear Train
The middle sun gear rotates clockwise with the clutch (C3), but at a lower speed than the input shaft. Brake (B2) is activated and locks the planetary carrier. The long pinion gear rotates counter-clockwise which in turn rotates the ring gear counter-clockwise.
The counter drive gear rotates in a counter-clockwise direction with the ring gear at the same speed.
The counter driven gear is rotated in a clockwise direction which in turn drives the differential ring gear in a counter-clockwise direction.

NOTE:
Engine braking is available when this gear is selected.

Power Flow Neutral





X = Operating





X = Operating
In neutral, all the solenoids, except the 3 way solenoids, are energized and the clutches and brakes are all disengaged. This allows rotation from the input shaft to rotate the front planetary gear train without transferring any drive to the differential ring gear.

TRANSMISSION CONTROL MODULE (TCM)









The TCM (transmission control module) is located on the top of the transmission casing and is connected on the high speed CAN (controller area network) bus to send and receive information to and from other system modules.
The TCM (transmission control module) outputs signals to operate the transmission solenoid valves to control the hydraulic operation of the transmission.
The ECM (engine control module) supplies the engine management data on the high speed CAN (controller area network) bus system. The TCM (transmission control module) requires engine data to efficiently control the transmission operation, using for example; crankshaft torque, engine speed, accelerator pedal angle, engine temperature etc.
The TCM (transmission control module) processes signals from the transmission speed and temperature sensors, ECM (engine control module) and other vehicle systems. From the received signal inputs and pre-programmed data, the TCM (transmission control module) calculates the correct gear, torque converter clutch setting and optimum pressure settings for gear shift and lock-up clutch control.
The steering angle sensor and the ABS (anti-lock brake system) module also supply data to the TCM (transmission control module) on the high speed CAN (controller area network) bus system. The TCM (transmission control module) uses data from these systems to suspend gear changes when the vehicle is cornering and/or the ABS (anti-lock brake system) module is controlling braking or traction control.
The TCM (transmission control module) is positioned over the transmission selector shaft which protrudes through an oil seal on the top face of the main transmission casing. The shaft locates in a rotary position sensor and turns the sensor in the appropriate direction. The Gear Shift Module (GSM), located above the TCM (transmission control module), rotates the shaft when a selection is made by the driver using the rotary TCS (transmission control switch). The rotary position sensor is a Hall effect sensor which outputs a specified voltage relating to the selected TCS (transmission control switch) position.
The transmission is controlled by a 'shift by wire' system. The TCS (transmission control switch) is connected to the TCM (transmission control module) and the GSM on the high speed CAN (controller area network) bus. Driver selections made on the TCS (transmission control switch) are passed via CAN (controller area network) messages to the GSM and the TCM (transmission control module). The GSM contains a rotary actuator which responds to driver selections and rotates the selector shaft in the appropriate direction.
If the TCM (transmission control module), GSM or transmission requires replacement, a setting procedure must be performed using a Land Rover approved diagnostic system to allow the TCM (transmission control module) to learn the neutral position of the transmission. The TCM (transmission control module) uses the neutral position as a reference point for each of the gear positions P, R, N, and D.

GEAR SHIFT MODULE (GSM)









The GSM is mounted on a bracket on the top of the transmission, above the TCM (transmission control module). The GSM Is secured to the bracket with four bolts.
The GSM contains an integrated actuator which automatically controls the transmission gear selection in response to the 'gear selection' signal transmitted from the TCS (transmission control switch). The GSM selects the requested gear based on all external parameter conditions being correct. The actuator drives a small connecting shaft which is located on top of the transmission selector shaft (above the TCM (transmission control module)).
The GSM transmits a signal to inform the driver of the selected gear, illuminating the TCS (transmission control switch)
LED (light emitting diode) 'PRNDS' and the instrument cluster displays. The gear position display in the instrument cluster has two modes; one mode displays P, R, N, D or S and the second mode displays the manual gear 1, 2, 3, 4, 5 or 6 when using the Land Rover CommandShift feature. The GSM monitors the TCS (transmission control switch) position, TCM (transmission control module) engaged gear, lock status and the GSM actuator position to control the displays.
Emergency Park Engagement
The GSM has an emergency park engagement feature to place the transmission into 'Park' in the event of a system fault. This function provides an external power input from the auxiliary battery module to the GSM, operating a motor which in turn rotates a cam which releases a spring loaded mechanism, placing the transmission into 'Park'.

Park Lock Control Strategy
The GSM controls the park lock function via CAN (controller area network) messages to the TCS (transmission control switch).
The park lock control strategy is processed by the GSM. Park lock is activated when the TCS (transmission control switch) is in Park unless the brake pedal is pressed and the engine is running.
Alternatively if the engine is running and the TCS (transmission control switch) is placed in Park while the vehicle speed is too high, the TCS (transmission control switch) remains unlocked. When the speed decreases below a set threshold or the engine is switched off, the TCS (transmission control switch) Park lock function is activated.
A brake pedal status signal is received by the GSM on the CAN (controller area network) bus from the ECM (engine control module). If the ECM (engine control module) signal is not available the ABS (anti-lock brake system) module provides back up information.
The GSM activates the Park lock when in Neutral unless the brake pedal is pressed. The lock request is ignored if the vehicle speed is greater than 6mph (10kph). When Neutral is selected, the lock is not activated for 2 seconds. This function allows the driver to move the TCS (transmission control switch) from R to D without the possibility of the Park lock being activated.
Manufacturing Mode
A new GSM is delivered in manufacturing mode. The module will function normally except Park selection is prevented.
In service, when replacing the GSM, the new module is supplied with manufacturing mode activated. The new module is programmed to the vehicle using a Land Rover Approved diagnostic system. Manufacturing mode is de-activated after the programming application learn process is complete.
Auxiliary Battery Module









The auxiliary battery module is a back up power supply system which supports automatic transmission Park selection, in the event of a system failure, by controlling the emergency park engagement feature of the GSM.
The auxiliary battery module system consists of a reserve battery and a module. The module has the following primary functions:
- Determine when to deploy the emergency park engagement function
- Provide the input signal to the GSM to activate the emergency park engagement system
- Provide emergency power and communication to the TCM (transmission control module) during an emergency park engagement event
- Reserve battery charging.
The auxiliary battery module manages the reserve battery charging process, keeping the voltage charge level within a narrow window. The charging strategy is designed to extend the reserve battery service life (approximately four years).
During a vehicle power interruption the auxiliary battery module supplies emergency power to the TCM (transmission control module) maintaining a primary line of communication via the LIN (local interconnect network) bus. This function provides the auxiliary battery module with information to determine the selected gear of the vehicle transmission.
The auxiliary battery module activates the emergency park engagement feature in the event that the GSM is unable to select Park.
The emergency park engagement function activates under the following conditions:
- A mechanical problem within the primary drive in the GSM exists
- The power supply to the GSM is interrupted
- Power supply to the TCS (transmission control switch) is interrupted and the driver is unable to select Park
The auxiliary battery module monitors the following primary input signals to determine if emergency park engagement should be triggered:
- Power mode
- Vehicle speed
- Gear position
The input signals are transmitted on the high speed CAN (controller area network) network to the TCM (transmission control module) which processes and sends the data to the auxiliary battery module via the LIN (local interconnect network) bus. If a fault exists on the LIN (local interconnect network) bus the auxiliary battery module uses the vehicle battery voltage as a trigger for emergency park engagement activation.
If the vehicle battery voltage drops below 10.5V, and the LIN (local interconnect network) communication is lost or corrupt, the auxiliary battery module activates the emergency park engagement function.
Diagnostics
GSM failure will primarily result in the system inability to perform gear shifts between the PRND positions. It will not be possible to complete the position learning process correctly. This will be reflected to the driver by either no LED (light emitting diode) activity or flashing of the PRND illumination position depending on the position in which the system has failed. The TCS (transmission control switch) may be locked to prevent the driver from attempting further shifts in the failure condition.
TCS (transmission control switch) failure will result in no LED (light emitting diode) activity of the PRND illumination position, refusal of the TCS (transmission control switch) to rise, or the TCS (transmission control switch) rising when the conditions are not correct. The TCS (transmission control switch) may become locked in any position.
Auxiliary battery module failure can result in a loss of LIN (local interconnect network) communication with the TCM (transmission control module) and automatic selection of the emergency park engagement system.
All failure modes, which result in a loss of functionality, will cause a "Gearbox Fault" warning being displayed in the instrument cluster.
Emergency Park Release (Service Mode)
There is no mechanical provision to remove the vehicle from Park in the event of a system fault. However, a service mode is available which allows the TCS (transmission control switch) to rise without the engine running in order to permit Neutral selection in fault conditions.
The following procedure places the system into service mode:
- Hold the '+' gear shift paddle and depress the brake pedal continually for 10 seconds after the ignition has been switched on
- The system will remain in service mode until the ignition is switched off or the engine is started

NOTE:
If there is a system power failure and the service mode function cannot be activated the only option available to remove the vehicle from Park is to remove the GSM unit from the vehicle. Once the GSM is removed the selector shaft can be manually rotated to the Neutral position. Refer to the relevant service repair procedure for access details.

CAUTION: Before the vehicle is driven and returned to the customer, the GSM gear position learning process must be completed using a Land Rover Approved diagnostic system. This MUST be completed any time the GSM is removed or replaced to ensure that position selection accuracy is maintained. Premature wear to the transmission or failure to select Park may result if the learning process is not performed.

INSTRUMENT CLUSTER

NOTE:
The following illustration shows the display when the transmission is in CommandShift mode. PRNDS is displayed during normal transmission operation.





The instrument cluster is connected to the TCM (transmission control module) via the high speed CAN (controller area network). Transmission status is transmitted by the TCM (transmission control module) and displayed to the driver in the instrument cluster. For additional information, refer to Instrument Cluster Locations
Malfunction Indicator Lamp (MIL)
The MIL (malfunction indicator lamp) is located in the upper LH (left-hand) corner of the instrument cluster, within the tachometer. Transmission related faults which may affect the vehicle emissions output will illuminate the MIL (malfunction indicator lamp).
The MIL (malfunction indicator lamp) is illuminated by the ECM (engine control module) on receipt of a relevant fault message from the TCM (transmission control module) on the CAN (controller area network). The nature of the fault can be diagnosed using a Land Rover approved diagnostic system which reads fault codes stored in the memory.
Transmission Status Display
The transmission status display is located in the central LCD (liquid crystal display) message display in the instrument cluster. The display shows the selected P R N D S position and in the case of manual 'CommandShift' mode, the selected gear.

DRIVING MODES
A number of different driving modes are available. Some can be selected by the driver and some are automatically initiated by the TCM (transmission control module) to adapt to different driving conditions.
- Normal
- Sports
- Manual 'CommandShift'
- Cooling
- Hill Descent Control (HDC)
- Cruise
- Limp home
- Coast
- Fast off recognition
- Uphill and Trailer
- Downhill
- Wide Throttle
- Terrain Response
- Reverse lock-out
- Kick-Down
- Shift Adapt Under Braking
- Corner Recognition
- Road Gradient Recognition
- Driver Type Recognition