It is a high-tech survival driveline component, and not commonly accepted that a clutch is a safety
critical item in the operation of a truck or light vehicle. Clutch failure can and does occur at the most
in-opportune time, which can place a heavy 56-ton combination with its cargo at risk on the road.
The resultant loss of vehicle productivity also must be considered - this could easily amount to
transport revenue losses of R16 000 for one day (R16/km).
Valuable perishable cargo, a load of sheep or fresh fish, adds to the nightmare of clutch failure in
road transport.
As the transmission component connecting the engine to the gearbox, the clutch is a driver’s
servant. A clutch ‘absorbs the abuse of forward and reverse thrust forces in terms of the way the
driver is trained or perceives the situation.
The lightness of a clutch pedal in modern truck and car drivelines tends to let drivers take the
existence of complex clutch componentry for granted. In fact, the driver is only likely to
acknowledge the clutch’s existence due to a tired left leg from working the pedal too often in stop-
start traffic.
The design parameters for today’s clutch demands a high level of technological inputs - the kW
power output from light vehicles is increasing, and Nm torque is spiralling upwards on heavy duty
truck engines. In the eighties the average diesel engine torque requirement for moving 50 tons gross
combination mass (GCM) was 1400 Nm - in the nineties this is now around 2500 Nm at 56 tons GCM.
All of this means that the modern clutch must provide a reliable clamp load to avoid slipping, and a
release load that matches the driver’s expectation for lightness of operation. The rotating mass of a
clutch in the driveline, weighing up to 70 kg, also must be finely balanced to avoid torsional
vibrations and driveline damage.
Considering the elements of road safety, consistent reliability, high demands for productivity, heat,
friction and ever-changing driver, load and road conditions, the demand for high-tech quality in
clutch design cannot be over-emphasised. Fleet management should not rely on recovery trucks or
emergency field work when it comes to clutch replacement or repairs. It is for these reasons that
Isuzu is the leading truck brand for Automated Manual Transmissions (AMT).