Page 141 of 378

Allison 2500
WARNING: To avoid sudden, unexpected vehicle movement
and possible personal injury or death:
1. Bring the vehicle to a complete stop.
2. Shift the transmission into positionN.
3. Apply the parking brake and make sure it is holding properly.
4. Turn the engine off when you leave the vehicle.Never leave the
vehicle unattended when the engine is running.
This transmission is available with a column-mounted gearshift lever. The
gear positions are displayed on the RNDL in the instrument cluster.
Allison 3000
Note:For more information regarding this transmission, see the separate
Allison 3000 Series Operator’s Manual.
The Allison 3000 series offers two shift modes: Performance and
Economy.
Performance mode gives the best all-around transmission operation. The
transmission defaults to this mode when you start the engine. Pressing
MODE on the shifter switches to Economy mode and illuminates the
Mode ON lamp.
Economy mode provides operation at lower engine RPM while
maintaining adequate performance.
If the engine speed is above idle when a gear is selected using the
shifter, the vehicle does not move; the shifter must be moved to re-select
a gear after the engine speed returns to idle.
Torque Lock
If your vehicle is parked on an incline and positionPis not properly
engaged (the parking brake is not applied before the transmission is
shifted into positionP),the weight of the vehicle may generate an
excessive amount of torque on the parking pawl, making it difficult to
shift the transmission out of positionP.Hold the brake pedal down while
shifting out of positionP,then release the parking brake.
140Transmission
2013 F-650/750(f67)
Owners Guide gf, 2nd Printing, March 2013
USA(fus)
Page 143 of 378

selector to positionNand then back into gear. The PTO should never be
engaged by clashing the gear teeth. This may damage the PTO unit and
the transmission PTO drive gear teeth, resulting in further damage to the
transmission and PTO.
PTO Operation with Vehicle Stationary
WARNING:When the PTO is operated with the vehicle
stationary, the transmission must be placed in positionNwith the
parking brake set. If the transmission is not in positionNand 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.
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 positionN.
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.
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.
142Transmission
2013 F-650/750(f67)
Owners Guide gf, 2nd Printing, March 2013
USA(fus)
Page 144 of 378

To engage the PTO unit, stop the vehicle and place the transmission in
positionN.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).
REAR AXLES
Gross Axle Weight
WARNING:Exceeding these ratings by overloading can cause
component failure resulting in property damage, personal injury
or death.
Your truck has gross axle weight, gross vehicle weight and gross
combination weight ratings. Do not exceed these ratings.
Locking or Limited-Slip Differentials
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
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.
Driver-controlled Differential Lock
Note:Never use the differential lock at vehicle speeds above 25 mph
(40 km/h).
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
(under-steer).
Transmission143
2013 F-650/750(f67)
Owners Guide gf, 2nd Printing, March 2013
USA(fus)
Page 155 of 378
Trailer Air Supply and Parking Brake Modular Controls
(If Equipped)
The trailer air supply valve delivers
air to the trailer supply and
automatically pops out, shutting off
the trailer supply, if pressure
decreases to approximately 35 psi
(249 kPa).
The parking brake controls the
spring brakes on the tractor. When
the knob is pulled out, it causes the
trailer supply valve to pop out,
applying both the tractor and trailer
parking brakes. The trailer brakes
may be independently released by
pushing only the trailer air supply
valve in.
Initial Charge
With the air system completely discharged, both knobs (A and B) are
out. When the air pressure reaches 70 psi (483 kPa), the trailer air
supply (A – red knob) may be pushed in and should stay in, charging the
trailer air system and releasing the trailer brakes.
B
AB
A
154Brakes
2013 F-650/750(f67)
Owners Guide gf, 2nd Printing, March 2013
USA(fus)
Page 156 of 378
The parking brake (B – yellow knob) can now be pushed in and supply
air to the tractor spring brakes, releasing them.
Normal Driving Position
With both knobs pushed in, air is supplied to both trailer and tractor
spring brakes and all brakes are released.
B
A
B
A
Brakes155
2013 F-650/750(f67)
Owners Guide gf, 2nd Printing, March 2013
USA(fus)
Page 157 of 378
System Park
With both knobs pushed in (normal driving position), the parking brakes
for both the tractor and trailer can be applied by pulling the parking
brake knob (B) out, exhausting air from the tractor spring brakes,
simultaneously causing the trailer air supply valve to pop out, applying
the trailer brakes.
Trailer Charge
If both knobs are out, and you want to recharge the trailer while leaving
the tractor spring brakes applied, the trailer air supply (A) can be
pushed in to recharge the trailer air supply line. This mode may also be
used to park a combination vehicle with tractor spring brakes.
B
AB
AB
A
B
AB
A
156Brakes
2013 F-650/750(f67)
Owners Guide gf, 2nd Printing, March 2013
USA(fus)
Page 158 of 378

Automatic Application
If both knobs are pushed in and the brake system air pressure is reduced
to approximately 35 psi (249 kPa), the trailer air supply (A) knob
automatically pops out applying the emergency or parking brakes on the
trailer. If the trailer air supply (A) knob is manually held in and the air
pressure is reduced to approximately 30 psi (207 kPa), a tripper piston
within the valve moves, exhausting the trailer air supply, applying the
trailer brakes. Further reduction of air pressure, while holding the trailer
air supply knob in, causes the parking brake knob to pop out at 25 psi
(172 kPa).
Actuation of Trailer Park (Emergency) or Tractor Bobtail Position
To actuate the trailer brakes only, pull out the trailer air supply knob
(A). The trailer brakes are now applied whether emergency or spring
brakes are used on the trailer.
This mode is also used when the tractor or truck with trailer is used
during bobtail operation.
B
A
B
A
Brakes157
2013 F-650/750(f67)
Owners Guide gf, 2nd Printing, March 2013
USA(fus)
Page 159 of 378

PARKING BRAKE
Hydraulic Brakes
WARNING:Do not use the gearshift selector in place of the
parking brake. Always set the parking brake fully AND make sure
the gearshift selector is in positionRfor vehicles equipped with a
manual transmission or positionP (if equipped)orNfor vehicles
equipped with an automatic transmission. Use of wheel chocks is also
recommended in hilly or off-road usage. Unexpected and possible
sudden vehicle movement may occur if these precautions are not taken.
WARNING:If the parking brake is fully released but the parking
brake warning lamp remains illuminated, the brakes may not be
working properly. See your dealer or a qualified service technician.
Apply the parking brake whenever the vehicle is parked. To set the
parking brake, pull the handle up until it snaps into the locked position.
When the parking brake is out of adjustment, seek service immediately.
The parking brake warning lamp in the instrument cluster
illuminates, and remains illuminated (when the ignition is
turned on), until the parking brake is released.
Push the palm release lever (A) on
the parking brake handle (B) and
push down as far as possible to
release the brake. Driving with the
parking brake on causes the brakes
to wear out quickly and reduces
fuel economy.
The parking brake is not recommended to stop a moving vehicle.
However, if the normal brakes fail, the parking brake can be used to stop
your vehicle in an emergency. Since the parking brake only applies
retardation to the rear wheels, the vehicle’s stopping distance increases
greatly and the handling of your vehicle is adversely affected.
Power Park (Hydraulic Brake Vehicles Only)
This feature uses a brake chamber mounted on the chassis to power a
spring-applied, hydraulically-released driveline parking brake.
P
A
B
158Brakes
2013 F-650/750(f67)
Owners Guide gf, 2nd Printing, March 2013
USA(fus)