header-to-tube stress and possible failure. Winter-
fronts should only be used when the ambient tem-
perature remains below 10°F (–12°C).
Driving on Flat, Dry Pavement
Use the following guidelines when driving on flat, dry
pavement.
•
If driving on flat, dry, open stretches, with a
light load, place the progressive braking switch
in the LOW position.
•
If you find you are still using the service
brakes, move the switch to a higher position
until you do not need to use the service brakes
to slow the vehicle.
•
If you are carrying a heavier load and road
traction is good, move the progressive braking
switch to the HIGH position.
•
Check your progressive braking switch often
for proper position, since road conditions can
change quickly. Never skip a step when oper-
ating the progressive braking switch. Always go
from OFF to LOW, and then to a higher posi-
tion.
Descending a Long, Steep Grade
An explanation of “control speed” may be helpful in
understanding how to use the engine brake system
while descending a grade. Control speed is the con-
stant speed at which the forces pushing the vehicle
forward on a grade, are equal to the forces holding it
back, without using the vehicle service brakes. In
other words, this is the speed the vehicle will main-
tain without using the service brakes or throttle.
CAUTION
Do not over apply the vehicle service brakes
when descending a long, steep grade. Excessive
use of the vehicle brakes will cause them to heat
up, reducing their stopping ability. This condi-
tion, referred to as “brake fade”, may result in
loss of braking, which could lead to loss of con-
trol of the vehicle, resulting in personal injury or
property damage.
Use the following guidelines when descending a
long, steep grade.
•
Before beginning the descent, determine if
your engine brake system is operating prop-
erly, by lifting your foot briefly off the accelera-
tor pedal. You should feel the system activate.
•
Ensure the progressive braking switch is in the
appropriate power position. Check your pro-
gressive braking switch often for proper posi-
tion, since road conditions can change quickly.
Never skip a step when operating the progres-
sive braking switch. Always go from OFF to
LOW and then to a higher position when on
slippery roads.
•
Do not exceed the safe control speed of your
vehicle. Example: You could descend a 6 per-
cent grade, under control at 10 mph (16 km/h)
without an engine brake, but at 25 mph (40
km/h) it requires an engine brake. You could
not descend that same hill at 50 mph (80
km/h) and still expect to remain under control.
Know how much slowing power your engine
brake can provide before descending hills, and
do not exceed a safe control speed.
Driving on Wet or Slippery Pavement
WARNING
To avoid injury from loss of vehicle control, do
not activate the engine brake system under the
following conditions:
•
on wet or slippery pavement
•
when driving without a trailer (bobtailing) or
pulling an empty trailer
•
if the tractor drive wheels begin to lock, or
there is fishtail motion after the engine
brake is activated
NOTE: On single trailers or combinations, a light
air application of the trailer brakes may be desir-
able to help keep the trailer stretched out. Fol-
low the manufacturer’s recommended operating
procedure when using the trailer brakes.
On wet or slippery pavement, start with the master
switch in the OFF position and use the gear you
would normally use under these conditions. If the
vehicle is maintaining traction, place the selective
braking switch in the LOW position and turn ON the
engine brake system. If the drive wheels are main-
taining traction and you desire greater slowing power,
move the braking switch to the next higher position.
However, if the tractor drive-wheels begin to lock, or
Engines and Clutches
7.5
To Next Page
Loading...
