TM 9-2320-283-10
2
2-22
KEY TO TRANSMISSION RANGE SELECTOR CONTROL AND
SLIDING FIFTH WHEEL CONTROL (Continued)
Automatic upshift and downshift points are influenced by the pressure of your
foot on the accelerator pedal. For example, when the accelerator pedal is fully
depressed, the transmission will automatically upshift near the governed speed
of the engine (2,100 rpm). A partially depressed accelerator pedal will cause
upshifts to occur at a lower engine speed.
Manual downshifts by depressing the button and moving the selector lever,
should be avoided when the vehicle is above the maximum speed obtainable
in the next lower gear. If a downshift or shift to REVERSE (R) is made at
too high a speed, the transmission hydraulic system automatically prevents
he shift from taking place until a safe lower speed is reached. Normally, service
brakes and the engine retarder should be used, as needed, to slow the vehicle
to an acceptable speed where the transmission may be downshifted, if needed.
SLlDING FIFTH WHEEL CONTROL
W A R N I N G
To prevent unintentional fifth wheel movement
during vehicle operation, ALWAYS BE SURE
CAB CONTROLLED SLIDING FIFTH
WHEEL LEVER IS IN THE LOCK POSITION
before vehicle is moved. To prove fifth wheel is
locked in position when coupled to a trailer,
place transmission selector lever in FIRST
GEAR (1), release park brakes and service
brakes, apply trailer brake hand control, and
tap accelerator pedal. This will cause the
tractor mounted fifth wheel to be pulled
sharply against the trailer mounted king pin.
Set park brakes, release trailer brake hand
control, and shift selector lever back to
NEUTRAL (N). Leave the cab and make a
visual check of the fifth wheel sliding plate to
verify it has not moved from the position
selected. This will also verify the trailer king
pin is securely locked into the fifth wheel
jaws. The control should also be in the LOCK
position any time the tractor is to be operation
even when not towing a trailer. NEVER MOVE
CONTROL TO THE UNLOCK POSITION
DURING NORMAL VEHICLE OPERATION
AS LOSS OF CONTROL CAN RESULT.
