Transmission General Description
The AF 40-6 automatic transmission is an electronic 6-speed
automatic transmission with lock-up. The transmission is mounted
directly against the engine and has a final drive with integrated
differential. The power unit is transverse mounted with front-wheel
drive. Gear positions P-R-N-D are selected with the selector lever
mounted in the centre console. Manual up/downshifting is
possible.
A special automatic transmission fluid must be used. The
transmission does not have an oil dipstick. The drain plug has an
extra, central check plug for checking the level that is connected
to a rising tube that reaches up to the correct level in the box.
Fill the oil through the conventional oil filler plug until the
level is correct and oil runs out of the check plug hole in the
rising tube. Measure the temperature when checking the level. The
temperature is read using a scan tool.
The AF 40-6 transmission has planetary gears, disc clutches,
brakes and torque converter with lock-up. The clutches and brakes
are applied hydraulically. The hydraulic system is controlled by
the Transmission Control Module (TCM) with the help of 8 solenoids,
2 shaft speed sensors and one oil temperature sensor. TCM
communicates on the high speed bus.
The TCM is mounted directly on top of the transmission and has
one connector to the car's electrical system and one directly to
the transmission. The gear position sensor is a Hall sensor and is
integrated in the control module. The TCM is mounted so that the
selector lever shaft goes through the control module. The selector
lever position can be calibrated with the scan tool, there is no
mechanical adjustment.
The TCM controls the transmission according to its programming,
the information from its own sensors and from other control
modules. The control module adapts its control of the solenoids to
compensate for normal wear in the transmission. The TCM is SPS
programmable.
Shifting
The TCM can determine whether to leave a gear engaged or to
change up or down. What it does is determined mainly by the gear
that is currently engaged, the speed of the output shaft and the
position of the accelerator pedal. The TCM changes gear by applying
or releasing a friction element in the transmission. The
application is regulated with PWM from the respective solenoid.
The gear can also be changed manually with the selector lever in
D position if using the Tap Up/Tap Down switch. The switch is
hardwired to the BCM which converts the information into a HSCAN
message that is used by the TCM.
Lock Up
The torque converter clutch is activated at a steady speed when
there is no need of torque amplification. If the brakes are applied
or acceleration increases, the function will be deactivated.
Safety Features
To protect the transmission there are temperature programs to
prevent overheating. The TCM can choose to raise the shift points
and activate lock up more often if the oil temperature is too
high.
The reverse gear will not be activated if the car is travelling
faster than 7 km/h. If the power supply to the solenoids fails, it
is still possible to drive the car. The gear position D/M gives 2nd
gear and P-R-N will work as usual. In case of a major fault in the
transmission, mechanical or electrical, the TCM will cut the supply
to the solenoids in a controlled manner (limp home).
In case the TCM detects a failure it will go into emergency
mode.
Special Gear Change Program
If an uphill gradient is detected, the gears will change at
higher engine speeds and each gear will remain engaged for longer
periods.
The Sport Mode can be engaged by a switch. Upon detecting the
sport mode request TCM adapts the shift lines in order to enable a
more progressive driving.
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