10.3.6 Semi-automatic transmission A number of different types of semi-automatic
transmission are either in use or under develop-
ment. An interesting system is the electronically
controlled clutch. This technology is a spin off
from formula 1 and top rally cars. The electronic
clutch was developed for these racing vehicles to
improve the get away performance and speed of
gear changes.
For production vehicles a system has been
developed which can interpret the driver’s inten-
tion. With greater throttle openings the clutch
operation changes to prevent abuse and driveline
damage. Electrical control of the clutch release
bearing position is by a solenoid actuator or elec-
tric motor with worm gear reduction. This allows
the time to reach the ideal take off position to be
reduced and the ability of the clutch to transmit
torque to be improved.
This technique has now been developed to the
stage where it will operate the clutch automat-
ically as the stick is moved to change gear. Sensors
are fitted to monitor engine and road speed as well
as gear position. The Ferrari Mondiale uses a sys-
tem similar to the one described here.
10.4 Diagnostics – automatic transmission 10.4.1 Systematic testing If the reported fault is that the kick down does
not operate proceed as follows.
1. Road test to confirm the problem.
2. Is the problem worse when the engine is hot?
Check the transmission fluid level! Has work
been done to the engine?
3. If fluid level is correct then you must investi-
gate further. Work on the engine may have
disturbed the kick down cable.
4. Check the adjustment/fitting of the kick down
cable.
5. Adjust if incorrect.
6. Run and repeat road test.
10.4.2 Test equipment Note: You should always refer to the manufac-
turer’s instructions appropriate to the equip-
ment you are using.
