2003 SSANGYONG MUSSO ECU

5A-24 AUTOMATIC TRANSMISSION
Transmission Control Unit(TCU)
The TCU is an in-vehicle micro-processor based transmission management system. It is usually mounted in the
vehicle cabin, under the instrument panel, under the seat, behind the side kick panels or under the floor in the
footwell on the passenger side. Different control units are supplied for different vehicle applications.The TCU contains:
Processing logic circuits which include a central microcontroller and a back-up memory system.
Input circuits.
Output circuits which control external devices such as the variable pressure solenoid (VPS), on/off solenoid
drivers, a diagnostics output and the driving mode indicator light.
The various items which make up the TCU are discussed below.
Processing Logic
Shift schedule and calibration information is stored in an erasable programmable read only memory (EEPROM).
Throttle input calibration constants and the diagnostics information are stored in electrically erasable programmable
read only memory (EEPROM) that retains the memory even when power to the TCU is disconnected. In operation the software continuously monitors the input values and uses these, via the shift schedule, to determine the required gear state, At the same time it monitors, via the solenoid outputs, the current gear state. Whenever the
input conditions change such that the required gear state is different to the current gear state, the TCU initiates a
gear shift to bring the two states back into line.
Once the TCU has determined the type of gear shift required the software accesses the shift logic, estimates the
engine torque output, adjusts the variable pressure solenoid ramp pressure then executes the shift.
The TCU continuously monitors every input and output circuit for short or open circuits and operating range. When
a failure or abnormal operation is detected the TCU records the condition code in the diagnostics memory and
implements a limp mode, The actual limp mode used depends upon the failure detected with the object to maintain
maximum driveability without damaging the transmission. In general input failures are handled by providing a default
value. Output failures, which are capable of damaging the transmission, result in full limp mode giving only third or
fourth gear and reverse. For further details of limp modes and memory retention refer to the Diagnostic Section.
The TCU is designed to operate at ambient temperatures between -40 and 85°C . It is also protected against
electrical noise and voltage spikes, however all the usual precautions should be observed, for example when arc welding or jump starting. TCU Inputs
To function correctly, the TCU requires engine speed, road speed, transmission sump temperature, throttle position
and gear position inputs to determine the variable pressure solenoid current ramp and on/off solenoid states. This
ensures the correct gear selection and shift feel for all driving conditions. The inputs required by the TCU are as follows: Engine Speed
The engine speed signal is derived from the tachometer signal line, a dedicated sensor or a Controlled Area Network (CAN).
Road Speed
4WD (Diesel) - The shaft speed signal is derived from the speedo sensor located on the transfer case. This signal is transmitted directly to the TCU.
4WD (Gasoline) - The speedo sensor sends the shaft speed signal to the engine control module (ECM). The
information is then transferred to the TCU via the CAN.
Transmission Sump Temperature
The transmission sump temperature sensor is a thermistor located in the solenoid wiring loom within the transmission.
This sensor is a typical NTC resistor with low temperatures producing a high resistance and high temperatures

5A-26 AUTOMATIC TRANSMISSIONInhibitor Switch
Throttle Position SensorThe throttle position sensor(TPS) is a resistance potentiometer mounted on the throttle body of the engine.
It transmits a signal to the TCU proportional to the throttle plate opening. The potentiometer is connected to the TCU by three wires:
5 volts positive supply, earth and variable wiper voltage.Throttle voltage adjustments are as follows:
Closed throttle voltage is 0.2V to 1.0V.
Wide open throttle voltage is 3V -4.7V.
These measurements are taken between pins 29 and 27 of the TCU.
Maintaining good shift feel through the transmission life span is dependant on having an accurate measure of
the engine throttle position. To achieve this the TCU
continuously monitors the maximum and minimum throttle
potentiometer voltages and, if a change occurs, stores the new voltage values.
However these limits will be lost and will require relearning
should a new TCU be installed, or the throttle calibration data
is cleared by the execution of a particular sequence, This last
instance depends on the installation, and reference should be
made to the Diagnostics Section of this manual. The relearningwill happen automatically Notice
Above figure of T.P.S. is for the diesel enginewhich is installed on the injection pump.
Gear Position Sensor
The gear position sensor is incorporated in the inhibitor switch mounted on the side of the transmission case.
(Refer to figure 3.5.) The gear position sensor is a multi-function switch providing three functions: Inhibit starting of the vehicle when the shift lever is in aposition other than Park or Neutral
Illuminate the reversing lamps when Reverse is
selected indicate to the TCU which lever position has been selected by way of a varying resistance (Refer to
table 3.3.)
Figure 3.5 - Inhibitor Switch

5A-86 AUTOMATIC TRANSMISSION
9. Remove the pump to case bolts using a multi-hex 8 mmspanner.
10. Using the pump puller No. 0555-332941, remove the pump.
11. Remove the input shaft, forward clutch cylinder, and the overdrive shaft as an assembly, withdrawing them through the front of the case.
12. Remove the C3 clutch cylinder and sun gears.
13. Remove the fronts band struts. Remove the front band.
14. Remove the two centre support retaining bolts using a T50 Torx bit.
15. Remove the centre support retaining circlip. Notice
Do not hammer the output shaft to remove the centre
support as this will cause permanent damage to the thrust bearing surfaces.
16. Remove the centre support, 1-2 one way clutch, planetary gear set and output shaft as an assembly.
17. Remove the parking rod cam plate. (T40 Torx bit).
18. Remove the rear band struts and remove the band. 4. Detach each end of the filter retaining clip from the valve
body and remove the filter.
5. Detach the wires from each solenoid and lay the wiring to one side.
6. Remove the valve body securing screws and remove the valve body from the case.
7. Remove the front servo cover circlip. Remove the cover and piston.Notice
The plastic servo block is retained by the piston return
spring only.
8. Where fitted, remove the flange yoke, and then remove the extension housing (RWD model).
Remove the adaptor housing (4WD model).

5A-94 AUTOMATIC TRANSMISSION
ASSEMBLY PROCEDURE The transmission is assembled in modular fashion and details of assembly for each module are given under the appropriatesubject. Refer to table 8.1 (at the end of Section 8.3) for the torque specifications to be applied, and to table 9.10 in section 9.6 for details of all special tools required, when performing
assembly procedures. Technicians overhauling these
transmissions will also require a selection of good quality Torxbit sockets, in particular numbers 30,40 and 50, and an 8 mm,10 mm and 12 mm double hex socket.
Transmission Notice
1. Ensure that the B1R circlip is fitted to the case. (If this is notfitted, the valve will peen its way into and through the separator plate.)
2. Ensure that the ‘E’ clip is fitted to the cross shaft.
3. Ensure that all aspects of the parking mechanism are working.
To assemble the transmission, proceed as follows:
1. Turn the transmission case upside down on the bench and mount it to the transmission cradle No.0555-331895.
2. Install all fittings, plugs and the breather, applying a sealant where applicable, Tighten the fittings to specifications.
Ensure that the breather is clear, and check that the lube fitting in the rear of the case is fitted and clear of obstruction.
3. Assemble the B1R valve and spring, and secure with the irclip. Refer to Ensure that the circlip is completely seatedin its groove.
4. Install the rear servo lever and pivot pin.
Notice The lever must pivot freely on its pin.

AUTOMATIC TRANSMISSION 5A-95
Notice
Care must be taken when applying sealant to ensure that it is
not applied between the pin and the lever.
5. Assemble the park rod lever, complete with the return springand pivot pin, applying a small amount of sealant to the
outer end of the pivot pin.Notice That the lever must pivot freely on its pin and the spring must return the park rod lever to its correct location.
6. Secure the pivot pin with the circlip. Notice The pawl must pivot freely on its pin.
7. Install the parking pawl pivot pin and spring.
8. Connect the park rod to the manual valve detent lever.Ensure the spring and cam collar is firmly installed on the rod.

AUTOMATIC TRANSMISSION 5A-99
Output Shaft and Gear Assembly
To assemble the output shaft and gear assembly (refer to (figure 8.19), proceed as follows:
1. Check that the output shaft bush is not won or damaged.Replace if necessary.
2. Check for damage to parking pawl teeth on the ring gear. Replace if necessary.
3. Check that the sealing ring grooves have not been damaged.
4. Lubricate the sealing rings with automatic transmission fluid.
5. Assemble the sealing rings to the output shaft with the scat cut uppermost.
6. If previously dismantled, assemble the ring gear to the output shaft and secure with circlip. Ensure that the circlip is firmly seated in its groove.
7. Fit the thrust bearing assembly No. 10 onto the output shaft using petroleum jelly.
8. Carefully install the output shaft assembly in the case to prevent damage to the sealing rings.
Rear Servo Assembly
To assemble the rear servo assembly (refer to figure 8.18), proceed as follows.
1. Check the servo piston ‘O’ rings and gasket for any damage.
2. Lubricate the servo piston ‘O’ rings with automatic
transmission fluid, and fit the ‘O’ rings to the piston grooves.
3. Assemble the piston to the cover, ensuring t h a t ‘O’ ring
compression is adequate but not excessive.
4. Align the spring on the piston spigot, then position the rear servo rod into the spigot.NoticeDo not use petroleum jelly on the gasket.
5. Assemble the gasket to the cover and fit the assembly to the case.
6. Apply Loctite 567 sealant to the bolts. Install the bolts and tighten to specification.

5A-106 AUTOMATIC TRANSMISSION
29. Align the tangs and fit the nylon thrust washer onto theC4 hub. Refer to figure 8.27.
30. Align and fit the C4 hub to the C2 clutch and the OWC assembly.
31. Check the rotation of the C2 hub. While holding the C4 hub, the C2 hub should rotate in the clockwise
direction and lockup in the anti-clockwise direction when
viewed from the C2 hub. Refer to figure 8.27.
Figure 8.27 - C2 - Hub Rotation
32. Apply petroleum jelly to the No. 5 thrust bearing and fitit to the C4 hub. Refer to figure 8.19.
33. Remove the C2 clutch plates from the clutch cylinder.
34. Fit the thrust plate over the cylinder inner hub. Refer to figures 8.24 and 8.19.
35. Engage the C2/C4 clutch hub assembly in the C4 clutch plates.
36. Install the C2 clutch plates.
37. Install the C3 hub and secure it with the circlip, ensuring that the circlip is firmly seated in its groove.Refer to figure 8.32. Figure 8.26 - Typical C2 Clutch Pack Clearance
26. Check the clutch pack clearance using only the weight
from tool No.0555-331900. Refer to figure 8.26.NoticeWith the clutch pack supporting a 2 kg weight, the dimension from the C3 clutch hub locating step to the friction plate is to be between 0.80-1.05 mm.
27. Use selective plates to achieve the correct specification. If new friction plates are being fitted, remove the clutch
pack and soak the friction plates in ATF for a minimum
of 5 minutes prior to reassembly. NoticeThe clutch pack clearance must be taken before the
elements are soaked in ATF.
28. Lubricate and fit the 3-4 OWC and end caps to the C2 hub.

AUTOMATIC TRANSMISSION 5A-111
7. Coat the small nylon thrust spacer with petroleum jelly andinstall it over the overdrive shaft. Refer to figure 8.19.
8. Carefully fit the overdrive shaft into the C1 cylinder so as not to damage the sealing ring.
9. Fit the small bronze C1 hub thrust washer in place with petroleum jelly. Refer to figure 8.19.
10. Check the input shaft for any defect. Fit the input shaft into the cylinder and secure it with the circlip, ensuring
that the circlip is completely seated in the groove.
11. Coat the sealing rings with petroleum jelly and fit onto the input shaft.
12. Assemble the C1/C2/C4 clutch assembly to the C3 clutch and sun gear assembly. Refer to figures 8.32 and 8.33.
13. Install this assembly in the transmission case.