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1. OVERVIEW
The six speed automatic (M78) transmission is
available in two variants: four wheel drive and
two wheel drive.
The transmission has the following features:
Six Forward Speeds
One reverse gear
A torque converter with an integral converter lock-up clutch
Electronic shift and pressure controls
A single planetary gear-set
A double planetary gear-set
Two hydraulically controlled brake bands
Three multi-plate clutches
All hydraulic functions are directed by electronic solenoids to control: -
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Engagement feel
Shift feel
Shift scheduling
Modulated torque converter clutch applications ·
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The transmission contains fully synthetic automatic transmission fluid (ATF) and is filled for life; therefore
it does not require periodic servicing.
Engine power reaches the transmission via a torque converter with integral converter lock-up clutch.
The six forward gears and one reverse gear are obtained from a single planetary set, followed by a
double planetary set. This type of gear-set arrangement is commonly known as Lepelletier type gear-set.
The automatic transmission is electronically controlled. The control system is comprised of the following
elements:
External transmission control unit (TCU)
Internal embedded memory module (EMM)
Input and output speed sensors
Valve body unit comprised of four on/off solenoid valves and six variable bleed solenoids
Torque converter -
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2) Cooling System
The transmission cooling system ensures rapid warm-up and constant operating temperature resulting
in reduced fuel consumption and refined shift quality.
It also includes a cooler by-pass within the hydraulic system to allow sufficient cooling and lubrication to
the transmission drivetrain in the event of a blockage in the transmission cooler.
Gear Shift ▶
Coastdown ▶
Torque Demand ▶ Transmission gear change is controlled by the TCU. The TCU receives inputs from various engine and
vehicle sensors to select shift schedules and to control the shift feel and torque converter clutch (TCC)
operation at each gear change
Coastdown downshifts occur at 0% accelerator pedal when the vehicle is coasting down to a stop. To
reduce the shift shock and to improve the shift feeling during downshift, TCU electronically controls the
transmission.
Torque demand downshifts occur (automatically) when the driver demand for torque is greater than the
engine can provide at that gear ratio. If applied, the transmission will disengage the TCC to provide
added acceleration.
3) Shift Strategy
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2) Mode “M” (Manual Shift Mode)
This allows the driver to define the highest possible gear by selecting "+" or "-" on the gear selector when
the lever is in the "M" position. When the lever is first moved to the manual "M" position the transmission
will select the lowest possible gear.
When maximum engine rpm is reached the transmission will upshift automatically regardless of the
driver selected limit. 4WD models with low range will not automatically upshift when low range is
selected.
1st gear position ▶
2nd gear position ▶
3st gear position ▶
4th gear position ▶
5th gear position ▶
6th gear position ▶Use on a rugged road, mountain path and steep hill. Engine braking effect on steep hill is
available. -
Use on a long and gentle slope. 2-1 automatic kickdown shift is available. Engine braking effect is
available. -
Use on a long and gentle slope. 3-2 and 2-1 automatic kickdown shift is available. Engine
braking effect is available. -
Use on a long and gentle slope. 4-3, 4-2 and 4-1 automatic kickdown shift is available. -
5-4 and 5-3 automatic kickdown shift is available. -
6-5 and 6-4 automatic kickdown shift is available. -
Kickdown Function
If you need to accelerate rapidly, depress the accelerator pedal completely to the floor.
Then, a one- or two-lever gear will automatically be engaged. This is called the Kickdown function.
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4. LIMP HOME MODE
In case of transmission malfunction ▶
If a serious fault occurs in the automatic transmission, the TCU enters the limp home mode to
secure safe driving and protect the automatic transmission.
As power is no longer supplied to the solenoid, the current basic function (P, R, N, D) is
maintained and the 4th gear can be maintained only by the operation of the hydraulic system
without electrical operation.
The ECU communicates with other electric modules with CAN. If a serious fault occurs, the
transmission automatically enters the limp home mode for service.
The TCU monitors all factors which can affect to the performance of the transmission and
diagnose the system according to OBD II regulation. 1.
2.
3.
4.
In case of overheated transmission ▶
The TCU enters the limp home mode when the batter voltage drops below 8 V.
If the transmission is overheated, the shift pattern is changed to the hot mode to cool the
transmission more efficiently.
While the transmission is overheated, the selector lever symbol and engine temperature warning
lamp on the instrument cluster blink until the transmission is cooled down to the normal operation
temperature. If the transmission is excessively overheated, the gear cannot be shifted but
remains in the neutral position. 1.
2.
3.
Towing the vehicle with A/T ▶
The best way to transport the vehicle is to load it to a truck and transport it, especially if the vehicle is
4WD.
If towing the vehicle with the propeller shaft connected, the transmission or oil pump of transfer case
may malfunction, resulting in internal damage due to poor lubrication. -
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5. ELECTRONIC CONTROL SYSTEM
1) Overview
The transmission control unit (TCU) and its input/output networks control the operations of transmission:
Shift timing
Line pressure
Clutch pressure (shift feel)
Torque converter clutch -
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In addition, the TCU receives input signals from certain transmission-related sensors and switches. The
TCU also uses these signals when determining transmission operating strategy. Using all of these input
signals, the TCU can determine when the time and conditions are right for a shift, or when to apply or
release the torque converter clutch. It will also determine the pressure needed to optimise shift feel. To
accomplish this, the TCU operates six variable bleed control solenoids and four ON/OFF solenoids to
control the operations of transmission.
2) Transmission Control Unit (TCU)
The transmission control unit (TCU) is mounted under the driver's seat and controls the operation of the
transmission.
TCU processes the analog information from the internal sensors and the digital information through CAN
communication lines. TCU monitors all the input and output signals. If there is any failure, TCU changes
the system to “Limp Home Mode” and alerts to the driver through the warning lamp on the
instrument cluster.
(1) Hard-wired (Analog) Input/Output
Input/Output Data between TGS Lever and TCU ▶
Position and conditions of gear select lever
Driving moded (Winter or Standard) -
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Position of inhibitor switch - Input/Output Data between Inhibitor and TCU ▶
6 control signals for variable bleed solenoid
4 control signals for ON/OFF solenoid
Transmission input speed
Transmission output speed
Transmission oil temperature
EMM (Embeded Memory Module) -
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- Input/Output Data between Automatic Transmission and TCU ▶
Input/Output Data between Self Diagnostic Connector and TCU ▶
Various DTC codes and TCU information -
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Pressure Modulation ▶
To provide a higher level of shift comfort and durability, the hydraulic pressure in the shift related friction
elements of the transmission must be matched accurately to the input torque to transmission. This
hydraulic pressure is composed of a hydraulically pre-set basic pressure and a control pressure which is
set by one of the variable bleed solenoids.
The transmission input torque can be directly calculated from the following operating parameters:
engine torque signals
engine speed or any signal transmitted from ECU through CAN lines
converter slip -
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Separate pressure characteristics for each gear change make it possible to adapt precisely to the
particular shift operation.
5) Shift Mode Selection by TCU
The driver can select Standard (S) or Winter mode (W) with the mode switch. TCU automatically
changes the shift mode according to the transmission oil temperature, uphill or downhill gradient, and
altitude to keep the good driving conditions.
Standard Mode (S) ▶
Uphii and Downhill Mode ▶
Altitude Mode ▶ Standard Mode is selected when setting the mode switch in Standard (S) position with the gear select
<0093008c009d008c0099004700900095004702c8006b02c9004700880095008b0047009b008f008c0047009b009900880095009a00940090009a009a00900096009500470096009000930047009b008c00940097008c00990088009b009c0099008c004700
9000950047009500960099009400880093004700960097008c>rating range. Proper shift timing
provides the optimized fuel economy and good driving conditions.
In this mode, the operating points of torque converter lock-up clutch and the shifting points are adjusted
according to the vehicle weight.
In this mode, the shifting points are automatically adjusted according to the altitude to compensate the
engine torque changes due to barometric pressure and temperature.
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Variant Coding Options
(2) Detects the position of the shifting lever for the HDC operation
among ABS functions.
The HDC function operates only if the M/T shift lever is in forward or reverse position. Please refer to the
ABS section for the specific information related to the HDC.
Variant Coding Related to N Switch ▶
The N switch transmits information to the ECU through the CAN communication while New Rexton is
connected to the ECU through wires. Thus, if you set the variant coding in the engine ECU, you must do
it differently, and you must set the variant coding differently according to the vehicle category and
specification as below.
Neutral Signal Input None / Wire / CANWire /
Actyon & Kyron models with
manual transmission
New Rexton model with manual
transmission Manufactured after
04.09.15
BODY IN: after 154600
Automatic transmission & Rodius
model with automatic transmission
before 2006
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Operation ▶
Description Mode Conditions
Driving
mode2H 2 Wheel drive
(rear wheel)Rear-wheel drive mode. This is used under
normal or high-speed driving conditions on
public roads or highways.
4H 4 Wheel drive
(high speed)This is used under sandy, muddy or snow-
covered road conditions
4L 4 Wheel drive
(low speed)This is used for maximum traction.
When cornering with low speed in 4WD
condition, there could be tire dragging, some
mechanical shocks and resistances in
vehicle’s drive train. These are normal
conditions due to internal resistance in the drive
train when the 4WD system is properly working
Mode change2H←4H2 Wheel drive
↔4 Wheel driveShifting is possible while driving at the speed of
70 km/h or less
2H,
4H↔4L2 Wheel drive,
4 Wheel drive (high
speed)
↔4 Wheel drive
(low speed)For Automatic Transmission:
For Manual Transmission:
Stop the vehicle on level ground and
move the gear selector lever into the
“N” position. Turn the switch to the
desired position. ·
Stop the vehicle on level ground and
move the gear selector lever into the
“N” position. Then turn the switch to
the desired position while depressing the
clutch pedal. ·
To make the mode change easily, stop the
vehicle on level ground and turn the mode
switch to the desired position and move the
shift lever to "N"-"R"-"N" while depressing
the brake pedal.