freightliner Cargo Manual page 61

Clutches, Rear Axles, and Steering
Clutches
General Information
The major reason clutches wear out too soon is exces-
sive heat. Clutches are designed to absorb and dissi-
pate more heat than encountered in typical operation.
The temperatures developed in typical operation will not
break down the clutch friction surfaces. However, if a
clutch is slipped excessively, or required to do the job of
a fluid coupling, high temperatures develop quickly and
destroy the clutch. Temperatures generated between
the flywheel, driven discs, and pressure plates can be
high enough to cause the metal to flow and the friction
facing material to char and burn.
Slipping and excessive heat are practically nonexistent
when a clutch is fully engaged. But during the moment
of engagement, when the clutch is picking up the load,
it generates considerable heat. An incorrectly adjusted
or slipping clutch will rapidly generate sufficient heat to
destroy itself.
The most important items that a driver should be aware
of to ensure long service life of the clutch include: start-
ing in the right gear, recognizing clutch malfunctions,
and knowing when to adjust a clutch.
6.1
Clutch Operation
Starting the Vehicle in the Correct Gear
To drive forward, always start in first gear. After the
clutch is fully engaged, the engine should be acceler-
ated to the correct rpm for the upshift into the next
higher gear.
Gear Shifting Techniques
Many drivers upshift into the next gear, or even skip-
shift into a higher gear, before the vehicle has reached
the correct speed. This type of shifting is almost as bad
as starting off in a gear that is too high, since the en-
gine rpm and vehicle speeds are too far apart, requiring
the clutch to absorb the speed difference by generating
heat. For transmission operating instructions, see
Chapter 5.
Vehicle Overload, or Overloading the Clutch
Clutches are designed for specific vehicle applications
and loads. These limitations should not be exceeded.
CAUTION
Overloading will not only result in damage to the
clutch, but also to the entire powertrain.