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Engaging the clutch
•Always start in the proper gear.An empty vehicle can start in a
higher gear than a fully loaded vehicle. Starting in too high a gear can
cause clutch slippage and excessive heat and wear on the clutch. A
gear that starts the vehicle moving at idle speed is the correct gear. If
the engine has to be revved to get the vehicle going, the gear
selection is too high.
•Do not shift until the vehicle has reached the proper speed.
Upshifting before the vehicle has reached the proper speed can cause
clutch slippage and excessive heat and wear on the clutch.
•Never hold a vehicle on a grade with the clutch.This causes the
clutch to slip and can actually burn up the clutch.
•Never coast with the clutch disengaged.The high RPM
(sometimes over 10,000), can actually burst the facing material of the
clutch.
•Never engage the clutch while coasting.Re-engaging the clutch
after coasting may not only cause a great shock to the clutch, but the
whole drivetrain. Internal engine damage and/or clutch and flywheel
failure can result from this.
If the transmission is equipped with a ceramic clutch, you must start the
vehicle moving in first gear and engage the clutch before pressing the
accelerator at idle. Also, don’t try to slip the clutch by raising engine
RPM and riding or feathering the clutch pedal since this causes erratic
engagement which can cause engine stalling and potential serious
damage to driveline components.
Clutch brake (non-synchronized transmissions) - Vehicle stationary
A clutch brake is used to stop transmission input shaft rotation so that
the initial 1 (First) or R (Reverse) gear selection can be accomplished
when the vehicle is stationary and the engine is at idle speed. Clutch
brake application occurs in the last inch (25 mm) of clutch pedal travel.
When using the clutch brake, fully press the clutch pedal and shift the
transmission into 1 (First) or R (Reverse). If the transmission won’t go
into one of these gears, slowly release the clutch pedal while applying
light pressure on the transmission shift lever until it shifts into gear.
Note:After engagement of 1 (First) gear,do notuse the clutch brake
for upshifting or downshifting. If you do, clutch brake life shortens and
gear selection shift efforts may increase.
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Double-clutch procedures - non-synchronized transmissions
In order to properly upshift or downshift:
1. Press the clutch pedal to disengage the clutch.
2. Shift the transmission into neutral.
3. Release the clutch pedal.
If upshifting,wait until the engine speed matches the transmission
speed of the gear you are selecting.
If downshifting,accelerate the engine until the engine speed matches
the input speed of the gear you are selecting. Press the clutch pedal
immediately and shift into the desired gear, then release the clutch
pedal.
MANUAL TRANSMISSION OPERATION (IF EQUIPPED)
Manual transmission shift patterns
are displayed on either the shift
lever knob or the sun visor. Study
this information carefully before you
drive the vehicle even though you
may be familiar with similar units.
Do not attempt to drive the vehicle
without knowing the exact shift
pattern of the transmission. Consult
your authorized dealer if any questions exist as to the shifting
instructions posted in your vehicle.
Driving hints
The following driving hints are provided as a brief, general guide in
operating the different manual transmissions used in your vehicle.
•When shifting into 1 (First) or R (Reverse) with vehicle standing still,
quickly release and press the clutch pedal (if necessary to complete
gear engagement).
•Always use the lowest (or most appropriate) gear to start the vehicle.
•Always use a gear ratio low enough to allow the engine to operate
above the minimum engine operation speed range.
•Do not lug the engine.
•Do not slam or jerk the gearshift lever into gear.
•When more power is required, shift to a lower gear and accelerate the
engine near the governed speed.
R 1 3 5
4
6 2
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WARNING:Do not coast the vehicle with the clutch pedal
pressed or with the transmission in neutral. This practice could
result in loss of vehicle control.
To go forward
With the engine idling, press the clutch pedal in and shift into 1 (First).
Engage the clutch while pressing the accelerator to start forward.
Operate the clutch and upshift as required by driving conditions.
To go backward
Put the gearshift lever in R (Reverse) and engaging the clutch while
pressing lightly on the accelerator.
Shifting with a synchronized transmission
With the clutch pedal pressed in, use the 2 (Second) gear synchronizer
to stop the clutch disc rotation; this allows smooth engagement of 1
(First) or R (Reverse). To complete the gear engagement, it may be
necessary to apply light pressure to the gearshift lever during initial
engagement of the clutch. It takes a second or two to match gear speeds;
steady pressure on the gearshift lever helps the synchronizer perform its
job more quickly. If the gearshift lever is forced into position, this action
defeats the purpose of the synchronizer by causing gear clash.
Shifting with a non-synchronized transmission
Refer toClutch brakeandDouble clutch proceduresin theClutch
section of this chapter.
Operating the Eaton FS-5205A 5–speed transmission
This transmission is equipped with
five forward gears and one reverse;
gears 2–5 are synchronized. The
shift pattern is embossed on the
gear shift knob.
Do not shift the transmission into R (Reverse) while the vehicle is
moving as this could damage the transmission.
R 2 4
3 5 1
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Operating the Eaton FS–5406A, FS–5406N, FS–6406A and
FSO–6406A 6-speed transmissions
These transmissions are equipped
with six forward gears and one
reverse; all forward gears are
synchronized. The shift pattern is
embossed on the gear shift knob.
Do not shift the transmission into 1 (First) or R (Reverse) while the
vehicle is moving as this could damage the transmission.
Operating the Spicer ES56-7B and ES066-7B 7-speed transmissions
These transmissions are equipped
with seven forward gears and one
reverse; gears 2–7 are synchronized.
The shift pattern is embossed on
the gear shift knob.
Do not shift the transmission into 1 (First) or R (Reverse) while the
vehicle is moving as this could damage the transmission.
POWER TAKE-OFF (PTO) OPERATION (IF EQUIPPED)
Vehicles equipped with an Allison automatic transmission (except
Allison 3000 Series applications )
The PTO can be operated while the vehicle is standing or moving. To
engage the PTO, apply the brakes and shift to any gear other than N
(Neutral), then engage the PTO.
If engagement is prevented by the gear teeth not meshing properly,
release the brakes and allow the vehicle to creep slightly or shift the
selector to N (Neutral) and then back into gear. The PTO should never
be engaged by clashing the gear teeth as this may damage the PTO unit
and the transmission PTO drive gear teeth which could result in further
damage to the transmission and PTO.
R 1 3 5
4
6 2
2 4 6
3 5 71 R
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PTO operation with vehicle stationary
Stop the vehicle, idle the engine and set the parking brake. Make sure the
gear selector is in any forward drive range, then engage the PTO. After the
PTO is engaged, move the range selector to N (Neutral). Increase the engine
speed until the desired PTO operation speed is obtained. To disengage the
PTO after operation with the vehicle standing, release the throttle, allow the
drive equipment to come to a stop, and then disengage the PTO.
WARNING:When the PTO is operated with the vehicle
stationary, the transmission must be placed in N (Neutral) with
the parking brake set. If the transmission is not in N (Neutral) and is
equipped with a remote throttle control, an increase in engine speed
can overpower the parking brake and cause the vehicle to move,
possibly resulting in personal injury and/or property damage.
PTO operation while vehicle is moving
After the PTO is engaged for driven vehicle operation, shift to the desired
range and drive the vehicle. The speed of the PTO, during this period of
operation, always maintains direct relation to vehicle speed. PTO speed
decreases in relation to vehicle (transmission output) speed as shifts to a
higher gear occur. When operating the PTO while the vehicle is moving,
the PTO may be disengaged whenever it is no longer required. When there
is no load on the PTO gear, it can be pulled out of engagement.
Vehicles equipped with an Allison 3000 Series automatic transmission
The PTO drive gear is engine-driven and provides direct engine power.
The PTO can be operated when the vehicle is either stationary or
moving. The PTO gear is in constant mesh with the drive gear in the
torque converter housing. A friction clutch or constant drive is used to
transmit power to the PTO.
Vehicles equipped with a manual transmission
Transmission-mounted PTO units are available for local installation on
your vehicle. See yourBody Builder’s Layout Bookfor restrictions on
use and installation of PTO units.
To engage the PTO unit, stop the vehicle and place the transmission in N
(Neutral). Press the clutch and allow the gears to stop rotating, then
engage the PTO unit. The PTO can also be selected with the
transmission in gear as long as the clutch is pressed.
When operating the PTO with the vehicle stationary, first set the parking
brake (chock the wheels if the vehicle is on a hill or another uneven
surface).
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REAR AXLE INFORMATION
Axle operating temperature normally don’t exceed 100°F (38°C). If the
operating temperature exceeds 230°F (110°C), the rate of axle
lubrication oxidation increases and shorten the life of the lubricant and
seals, requiring axle lubrication changes to become more frequent to
preserve the axle. Extreme Pressure (EP) lubricants should not be run
consistently above 230°F (110°C).
Gross axle weight
Your truck has gross axle weight, gross vehicle weight and gross
combination weight ratings. Do not exceed these ratings.
WARNING:Exceeding these ratings by overloading can cause
component failure resulting in property damage, personal injury
or death.
Rear axles with locking or limited-slip differentials (if equipped)
If your vehicle is equipped with a locking or limited-slip differential, note
the following:
•Power is transmitted to the opposite wheel should one of the wheels
begin to slip.
•Both wheels must be raised off the ground should it be necessary to
operate one wheel with the vehicle stationary.
WARNING:If both wheels are not raised off the ground, the
one wheel that is not raised may pull the vehicle off its support,
possibly resulting in personal injury
Driver-controlled differential lock
To prevent the vehicle from moving when servicing the wheels, tires or
brakes, turn the engine off and raise all drive wheels of the locker
differential axle. Axles equipped with NoSPIN Detroit Locker differentials
deliver power to both wheels even when only one wheel is on the
ground.
WARNING:Failure to raise all drive wheels with this type of
differential could cause the vehicle to move unexpectedly,
resulting in property damage, personal injury or death.
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Care should be taken to avoid sudden accelerations when both drive
wheels are on a slippery surface.
WARNING:Sudden accelerations on slippery surfaces could
cause the wheels to spin, the vehicle to turn sideways on a
crowned road surface or in a turn, possibly resulting in loss of vehicle
control and personal injury.
Some drive axles have a driver-controlled differential lock. The
differential lock can lock or unlock the differential when the vehicle is
moving or stopped. When extra traction is required, the differential lock
provides full power to both axles.
When the differential is locked, the vehicle’s turning radius increases
(vehicle “under-steers”).
The differential can be locked or unlocked when the vehicle is moving at
a constant speed of under 25 mph (40 km/h) and while the wheels are
not slipping. The differential must not be locked when the vehicle is
traveling down steep grades and traction is minimal.
Note:Never use the differential lock at vehicle speeds above 25 mph
(40 km/h).
The differential lock and differential lock light automatically disengage at
speeds above 25 mph (40 km/h). The differential lock remains off until
either the vehicle is restarted or the differential lock switch is turned off
then back on.
Axle conversions
It is not recommended, or approved, for axle conversions to be
performed. However, it is understood that, on occasion, aftermarket
add-on axles are installed by others on the truck chassis which allow
operator control for weight transfer from other axles (i.e., air lift axles).
WARNING:When operating a loaded vehicle, the driver must
keep all adjustable axles on the ground at all times, supporting
their share of the vehicle’s load. Failure to do so can overload other
axles, tires, wheels, springs, steering components, brakes and frames,
resulting in early component failure, loss of vehicle control, possible
property damage and personal injury.
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TWO-SPEED REAR AXLE (IF EQUIPPED)
A two-speed rear axle allows the
driver to select a LO range for
greater pulling power and a HI
range for greater road speed and
fuel economy. These ranges can also
be used to provide additional steps
between transmission shifts when
driving on steep grades and/or fuel
economy may be factors.
Note:Do not shift between ranges
when the speed control is on.
WARNING:Never shift a two-speed axle when descending a
steep grade as this may cause loss of vehicle control and result
in personal injury.
Axle shifting
Manual transmissions
•To downshift,select the next lower gear, release and press the
accelerator pedal rapidly, or while holding the accelerator pedal down,
release and engage the clutch rapidly.Note:The clutch method is
recommended when driving at slower speeds.
•To upshift,keep the accelerator pedal down, select the next higher
gear, release the accelerator and pause until the axle upshifts.Note:
De-clutch for smoother axle upshifts when driving at slower speeds.
Automatic transmissions
•Use LOW when you drive a fully-loaded vehicle on a severe grade or
in congested traffic. To activate LOW, press the upper portion of the
switch.
•Use HIGH for all normal driving conditions with a lightly-loaded or
partially-loaded vehicle. To activate HIGH, press the lower portion of
the switch.
Note:You can’t split-shift with an automatic transmission. Also,
downshifting above 40 mph (64 km/h) may result in transmission or axle
damage.
To shift the axle from LOW to HIGH with the vehicle stopped, place the
transmission in N (Neutral), then press the lower part of the switch.
2SPD
LOW
HIGH
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