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 is located on the top of the transmission casing and is connected on the high speed CAN bus to send and receive information to and from other system modules.
The TCM outputs signals to operate the transmission solenoid valves to control the hydraulic operation of the transmission.
The ECM supplies the engine management data on the high speed CAN bus system. The TCM requires engine data to efficiently control the transmission operation, using for example; crankshaft torque, engine speed, accelerator pedal angle, engine temperature etc.
The TCM processes signals from the transmission speed and temperature sensors, ECM and other vehicle systems. From the received signal inputs and pre-programmed data, the 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 module also supply data to the TCM on the high speed CAN bus system. The TCM uses data from these systems to suspend gear changes when the vehicle is cornering and/or the Anti-lock Brake System (ABS) module is controlling braking or traction control.
The TCM is positioned over the manual shaft which protrudes through an oil seal on the top face of the main casing. The shaft locates in a rotary position sensor and turns the sensor in the appropriate direction when a selection is made using the selector lever. The rotary position sensor is a Hall effect sensor which outputs a specified voltage relating to the selected selector lever position.
The selector lever is connected to the automatic transmission and the rotary position sensor in the transmission by a Bowden cable. Movement of the selector lever moves the position switch via the Bowden cable and the switch position informs the TCM of the selected position; P, R, N or D. The sport and manual +/- 'CommandShift' switch passes sport or manual selections to the TCM on a Local Interconnect Network (LIN) bus. The TCM outputs appropriate information on the high speed CAN bus which is received by the instrument cluster to display the gear selection information in the message center.
If the TCM or transmission requires replacement, a setting procedure must be performed using a Land Rover approved diagnostic system to allow the TCM to learn the neutral position of the transmission. The TCM uses the neutral position as a reference point for each of the gear positions P, R, N and D.
CONTROL DIAGRAM
NOTE:
A = Hardwired; D = High speed CAN bus; O = LIN bus
INSTRUMENT CLUSTER
The instrument cluster is connected to the TCM via the CAN. Transmission status is transmitted by the TCM and displayed to the driver on one of two displays in the instrument cluster. For additional information, refer to Instrument Cluster Initial Inspection and Diagnostic Overview
Malfunction Indicator Lamp (MIL)
The MIL is located in the upper left hand corner of the instrument cluster, within the tachometer. Transmission related faults which may affect the vehicle emissions output will illuminate the MIL.
The MIL is illuminated by the ECM on receipt of a relevant fault message from the TCM on the CAN. The nature of the fault can be diagnosed using a Land Rover approved diagnostic system which reads fault codes stored in the TCM memory.
Transmission Status Display
The transmission status display is located on the right hand side of the instrument cluster, in the speedometer LCD display. The display shows the selector lever P R N D position and in the case of manual ('CommandShift') mode, the selected gear. When the selector lever is moved to the 'Sport' position, 'SPORT' is displayed below the CommandShift gear display.
Message Center Display
The message center is located below the speedometer and the tachometer at the bottom of the instrument cluster. The message center is a Liquid Crystal Display (LCD) to relay vehicle status information to the driver.For additional information, refer to Information and Message Center Description and Operation
CONTROLLER AREA NETWORK (CAN)
The high speed CAN broadcast bus network is used to connect the powertrain modules. The CAN bus is connected between the following electronic units:
High Speed CAN Bus
- TCM
- Instrument cluster
- Steering angle sensor
- Restraints control module
- Engine Control Module (ECM)
- ABS module
- Adaptive Front lighting System (AFS) control module
- Diagnostic socket.
The CAN bus allows a fast exchange of data between modules. The CAN bus comprises two wires which are identified as CAN high (H) and CAN low (L). The two wires are colored yellow/black (H) and yellow/brown (L) and are twisted together to minimize electromagnetic interference (noise) produced by the CAN bus messages. For additional information, refer to Communications Network Description and Operation
In the event of CAN bus failure, the following symptoms may be observed:
- Transmission operates in default mode
- Torque converter lock-up clutch control is disabled
- Gear position indication in instrument cluster LCD inoperative (this will also occur with any transmission fault).
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 to adapt to different driving conditions.
- Normal
- Sport
- 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
Normal
Normal mode is automatically selected by the TCM when the ignition is switched on. In this mode all automatic and adaptive modes are active. Normal mode uses gear shift and lock-up maps which provide the optimum of fuel consumption, emissions and driveability, depending on the driving style.
If the transmission is operated in sport mode or 'CommandShift' mode and the selector lever is moved back to the drive 'D' position, then normal mode operation is resumed.
Sport
Sport mode provides enhanced acceleration and responsiveness by the use of sports shift maps. This mode allows the transmission to down shift more readily and hold gears for longer at higher engine speeds.
Manual 'CommandShift'
Manual 'CommandShift' mode allows the transmission to operate as a semi-automatic transmission. The driver can change up and down the six forward gears with the freedom of a manual transmission.
Shift maps are provided to protect the engine at high speeds. The TCM will automatically change up to a higher gear ratio to prevent engine overspeed and change down to a lower gear ratio to avoid engine laboring and stalling.
When kick-down is requested the TCM shifts down to the lowest available gear. When the vehicle is stationary, the driver can select 1st, 2nd or 3rd to start off.
When moving from a standstill, upshifts can be pre-selected by making '+' selections with the selector lever for the number of upshifts required. The TCM then performs the requested number of upshifts when appropriate shift points are reached. For example; when moving off in 1st gear, if 3 '+' selections are made in quick succession, the TCM will automatically upshift through the gears to 4th gear as the vehicle accelerates, without any further selections being made.
Cooling
Cooling mode is activated when the TCM detects excessively high transmission fluid or engine coolant temperatures. When this mode is active torque converter lock-up is activated earlier to minimize a further rise in fluid and/or engine coolant temperature and assist fluid cooling.
Hill Descent Control (HDC)
The HDC mode assists the ABS module in controlling the downhill speed of the vehicle. When HDC is active, the TCM selects the most appropriate gear for the descent to maximize engine braking.
Maximum engine braking is applied using a shift map which initiates later upshifts and early downshifts.
Cruise
When speed control is activated, the TCM receives a speed control active message on the high speed CAN bus. The TCM activates a speed control map which minimizes up and down shifts.
Cruise mode is active when speed control is selected on and the transmission is in drive 'D', sport 'S', HDC or Terrain Response Grass/gravel/snow program. Unique cruise maps override the current mode to provide a smooth driving feel and mode reselection.
Limp Home
If a transmission fault is detected by the TCM, the TCM adopts a limp home strategy and a message 'TRANSMISSION FAULT LIMITED GEARS AVAILABLE' is displayed in the message center. If the fault has an effect on engine emissions, the MIL in the instrument cluster will also be illuminated.
In limp home mode, P, R and N functions operate normally (if the fault allows these selections) and the TCM locks the transmission in 3rd gear to allow the driver to take the vehicle to a Land Rover dealer or approved repairer. Torque converter lock-up is disabled and reverse-lock-out will not function.
If the vehicle is stopped and subsequently restarted in the limp home mode condition, the TCM operates normally until the fault which caused the condition is detected again.
Coast
Coast mode provides earlier downshifts during coasting dependant on output shaft deceleration rate to improve driveability and refinement by avoiding negative to positive driveline torque reversals transmission during the downshifts.
Fast Off Recognition
Fast off recognition is activated when the TCM detects that the driver has released the accelerator pedal quickly. This is detected by the TCM monitoring for a high level of negative pedal angle from ECM signals on the high speed CAN bus. If this condition is detected, the TCM holds the current gear ratio to allow the driver to complete the manoeuvre without the need for a downshift. The mode can remain active for a predetermined length of time or if the driving style remains passive.
Fast off recognition mode assists vehicle stability and is used in conjunction a lateral acceleration input during cornering to maintain the current gear until the corner is negotiated.
Uphill and Trailer
Uphill and trailer mode can be active when the transmission is operating in normal, sport or Terrain Response modes. When the vehicle is pulling a trailer or driving up an incline, the TCM detects the increased resistance by monitoring engine torque and speed signals received from the ECM on the high speed CAN bus and also transmission output shaft speed sensor signals. Uphill and trailer mode will provide downshifts to prevent a drop in transmission torque output and maintain driving force.
Downhill
Downhill mode can be active when the transmission is operating in normal, sport or Terrain Response modes. When the vehicle is descending an incline the TCM detects a reduction in resistance by monitoring engine torque and speed signals received from the ECM on the high speed CAN bus and also transmission output shaft speed sensor signals. Downhill mode assists engine braking by selecting an appropriate gear reducing the load required on the brakes.
Wide Throttle
Wide open throttle mode operates for part throttle upshifts and kick-down upshifts. It provides consistent wide open throttle upshift performance under all driving conditions. The full engine speed range is used in all driving modes; normal, sport, hill modes and Commandshift. Compensation is used for delays (hydraulic and electronic) in gear change request to gear change start to provide smooth changes and correct shift point correction.
Terrain Response
The Terrain Response system has a unique set of shift maps for each of the Terrain Response programs. These programs override existing modes; for example when HDC is active and the 'Sand', 'Mud and Ruts' or 'Grass/Gravel/Snow' programs are selected, a specific Terrain Response map is used, not the HDC mode shift map detailed previously.
Reverse Lock-Out
If the selector lever is moved from N to R and the vehicle is travelling forwards, reverse selection is prevented if the vehicle speed is 11 km/h (6.8 mph) or more. When reverse lock-out is activated, the clutch (C3) is released without energizing solenoid (SLC3), preventing the transmission from selecting reverse gear.
TRANSMISSION FAULT STATUS
If the TCM detects a fault with the transmission system, it will enter a default (limp home) mode to prevent further damage to the transmission and allow the vehicle to be driven. If possible reverse gear will be available and also 3rd gear only.
When a fault is detected a high speed CAN message is sent from the TCM and is received by the instrument cluster. The instrument cluster illuminates the MIL (if required) and displays an applicable message in the message center. For additional information, refer to Information and Message Center Description and Operation
Some transmission faults may not illuminate the MIL or display a fault message, but the driver may notice a reduction in shift quality.
ENGINE SPEED AND TORQUE MONITORING
The ECM constantly supplies the TCM with information on engine speed and torque through messages on the CAN bus. The TCM uses this information to calculate the correct and appropriate timing of shift changes.
If the messages are not received by the ECM, the TCM will implement a back-up strategy to protect the transmission from damage and allow the vehicle to be driven.
In the event of an engine speed or torque signal failure, the transmission will adopt the electrical limp home mode with the transmission operating in a fixed gear.
TOWING FOR RECOVERY
WARNING: Ensure that the remote handset remains docked whilst the vehicle is being towed. Removing the remote handset will engage the steering lock, which will prevent the vehicle from steering correctly.
If the engine cannot be run whilst the vehicle is being towed, there will be no power assistance for the steering or brakes. This will result in greater effort being required to steer or slow the vehicle, and greatly increased stopping distances.
CAUTION: The vehicle should only be towed with four wheels on the ground. Towing with two wheels on the ground will result in serious damage to the transmission.
The vehicle should only be towed for a maximum of 80 km (50 miles), at a maximum speed of 80 km/h (50 mph). Towing for a greater distance, or at a higher speed may result in serious damage to the transmission.
NOTE:
The recommended recovery method is by trailer or recovery vehicle.
Secure the towing attachment from the recovery vehicle to the front towing eye.
Insert the remote handset in the start control module and switch on the ignition by pressing the start/stop button once.
NOTE:
Leaving the ignition switched on for extended periods will cause the battery to drain.
Apply the foot brake, and move the selector lever to the neutral 'N' position. With the footbrake still applied, release the park brake. If electrical power to the selector is not available, the emergency release lever on the selector lever can be used to release the interlock solenoid.
The vehicle can be towed a maximum of 80 km (50 miles) at a maximum speed of 80 km/h (50 mph).
Park the vehicle on firm, level ground. Apply the park brake and move the selector lever to the park 'P' position.
Switch off the ignition and remove the remote handset.
CAUTION: The vehicle cannot be towed in a reverse direction.