gear range will improve performance and extend transmis-
sion life by reducing excessive shifting and heat buildup.
If the transmission temperature exceeds normal operating
limits, the powertrain controller will modify the transmis-
sion shift schedule and expand the range of torque con-
verter clutch engagement. This is done to prevent trans-
mission damage due to overheating.
If the transmission becomes extremely hot or is in danger
of overheating, the “Transmission Temperature Warning
Light” may illuminate and the transmission may operate
differently until the transmission cools down.
NOTE: Use caution when operating a heavily loaded
vehicle at low speeds (such as towing a trailer up a steep
grade, or in stop-and-go traffic) during hot weather. In
these conditions, torque converter slip can impose a sig-
nificant additional heat load on the cooling system. Down-
shifting the transmission to the lowest possible gear (when
climbing a grade), or shifting to NEUTRAL (when stopped
in heavy traffic) can help to reduce this excess heat
generation. During cold temperatures, transmission operation may be
modified depending on engine and transmission tempera-
ture as well as vehicle speed. This feature improves warm
up time of the engine and transmission to achieve maxi-
mum efficiency. Engagement of the torque converter clutch
is inhibited until the transmission fluid is warm (refer to
the “Note” under “Torque Converter Clutch” in this sec-
tion).
On models with 66RFE transmission, top overdrive gear is
also inhibited until the transmission fluid is warm, and
during extremely cold temperatures (-16°F [-27°C] or be-
low), operation may briefly be limited to first and direct
gears only. On trucks with AS66RC transmission, fifth and
sixth gears may be inhibited briefly on cold starts below
41°F (5°C), and during very cold temperatures (-4°F [-20°C]
or below), operation may briefly be limited to third gear
only. During this condition, the ability of the vehicle to
accelerate under heavily loaded conditions may be re-
duced. In all cases, normal operation will resume once the
transmission temperature has risen to a suitable level. 5STARTING AND OPERATING 331
• The transmission fluid has reached an adequate tem-
perature.
• The engine coolant has reached an adequate tempera-
ture.
• Vehicle speed is sufficiently high.
• The TOW/HAUL switch has not been activated.
• The driver is not heavily pressing the accelerator.
When To Use TOW/HAUL Mode
When driving in hilly areas, towing a trailer, carrying a
heavy load, etc., and frequent transmission shifting occurs,
push the TOW/HAUL switch to activate TOW/HAUL
mode. This will improve performance and reduce the
potential for transmission overheating or failure due to
excessive shifting. When operating in TOW/HAUL mode,
transmission upshifts are delayed, and the transmission
will automatically downshift (for engine braking) when the
throttle is closed and/or during steady braking maneu-
vers. The “TOW/HAUL Indicator Light” will illuminate in the
instrument cluster to indicate that TOW/HAUL mode has
been activated. Pushing the switch a second time restores
normal operation. Normal operation is always the default
at engine start-up. If TOW/HAUL mode is desired, the
switch must be pushed each time the engine is started. TOW/HAUL Switch334 STARTING AND OPERATING
WARNING!Do not use the “TOW/HAUL” feature when driving in
icy or slippery conditions. The increased engine brak-
ing can cause the rear wheels to slide, and the vehicle
to swing around with the possible loss of vehicle
control, which may cause an accident possibly result-
ing in personal injury or death.
Torque Converter Clutch
A feature designed to improve fuel economy has been
included in the automatic transmission on your vehicle. A
clutch within the torque converter engages automatically
at calibrated speeds. This may result in a slightly different
feeling or response during normal operation in the upper
gears. When the vehicle speed drops or during some
accelerations, the clutch automatically disengages. NOTE:
• The torque converter clutch will not engage (and 66RFE-
equipped trucks will not shift to sixth gear), until the
transmission fluid and engine coolant are warm [usually
after 1 to 3 miles (2 to 5 km) of driving]. Because engine
speed is higher when the torque converter clutch is not
engaged, it may seem as if the transmission is not
shifting properly when cold. This is normal. Using the
Electronic Range Select (ERS) shift control, when the
transmission is sufficiently warm, will demonstrate that
the transmission is able to shift into and out of Over-
drive.
• If the vehicle has not been driven for several days, the
first few seconds of operation after shifting the transmis-
sion into gear may seem sluggish. This is due to the fluid
partially draining from the torque converter into the
transmission. This condition is normal and will not
cause damage to the transmission. The torque converter
will refill within five seconds after starting the engine. 5STARTING AND OPERATING 335
4H
Four-Wheel Drive Lock High Range — This range locks the
front and rear driveshafts together forcing the front and
rear wheels to rotate at the same speed. Additional traction
for loose, slippery road surfaces only.
NEUTRAL (N)
Neutral — This range disengages both the front and rear
driveshafts from the powertrain. To be used for flat towing
behind another vehicle. Refer to “Recreational Towing” in
“Starting And Operating” for further information.
4L
Four-Wheel Drive Low Range — This range locks the front
and rear driveshafts together forcing the front and rear
wheels to rotate at the same speed. Additional traction and
maximum pulling power for loose, slippery road surfaces
only. Do not exceed 25 mph (40 km/h).
This transfer case is intended to be driven in the 2H
position for normal street and highway conditions such as
dry, hard surfaced roads.
When additional traction is required, the 4H and 4L
positions can be used to lock the front and rear driveshafts
together and force the front and rear wheels to rotate at the
same speed. This is accomplished by simply moving the gear selector to the desired positions once the appropriate
speed and gear requirements are met, refer to “Shifting
Procedure – Manually Shifted Transfer Case” in this section
for further information.
The 4H and 4L positions are intended for loose, slippery
road surfaces only. Driving in the 4H and 4L positions on
dry, hard surfaced roads may cause increased tire wear and
damage to the driveline components.
The “Transfer Case Position Indicator Light” in the instru-
ment cluster will alert the driver that the vehicle is in
four-wheel drive and that the front and rear driveshafts are
locked together. This light will illuminate when the transfer
case is shifted into either the 4H or 4L position. There is no
light for the 2H or NEUTRAL positions on some models.
When operating your vehicle in 4L, the engine speed is
approximately three times that of the 2H or 4H positions at
a given road speed. Take care not to overspeed the engine
and do not exceed 25 mph (40 km/h).
Proper operation of four-wheel drive vehicles depends on
tires of equal size, type and circumference on each wheel.
Any difference will adversely affect shifting and can cause
damage to the drivetrain. 5STARTING AND OPERATING 339
NOTE: Do not attempt to make a shift while only the front
or rear wheels are spinning, as this can cause damage to
driveline components.
Because four-wheel drive provides improved traction,
there is a tendency to exceed safe turning and stopping
speeds. Do not go faster than road conditions permit.
NOTE: Delayed shifts out of four-wheel drive may be
experienced due to uneven tire wear, low or uneven tire
pressures, excessive vehicle loading, or cold temperatures.
WARNING!You or others could be injured or killed if you leave the
vehicle unattended with the transfer case in the NEU-
TRAL position without first fully engaging the park-
ing brake. The transfer case NEUTRAL position disen-
gages both the front and rear drive shafts from the
powertrain and will allow the vehicle to roll, even if
the transmission is in PARK. The parking brake
should always be applied when the driver is not in the
vehicle.
Two-Wheel Drive High Range (2H)
Rear-Wheel Drive High Range — This range is for normal
street and highway driving on dry hard surfaced roads. Four-Wheel Drive High Range (4H)
Four-Wheel Drive High Range — This range locks the front
and rear driveshafts together forcing the front and rear
wheels to rotate at the same speed. Additional traction for
loose, slippery road surfaces only.
Neutral (N)
Neutral — This range disengages the front and rear
driveshafts from the powertrain. To be used for flat towing
behind another vehicle. Refer to “Recreational Towing” in
“Starting And Operating” for further information.
Four-Wheel Drive Low Range (4L)
Four-Wheel Drive Low Range — This range locks the front
and rear driveshafts together forcing the front and rear
wheels to rotate at the same speed. Additional traction and
maximum pulling power for loose, slippery road surfaces
only. Do not exceed 25 mph (40 km/h).
CAUTION!Do not use 4L (Low) range when operating the vehicle
on dry pavement. Driveline hardware damage can
result.340 STARTING AND OPERATING
NEUTRAL (N)
Neutral — This range disengages both the front and rear
driveshafts from the powertrain. To be used for flat towing
behind another vehicle. Refer to “Recreational Towing” in
“Starting And Operating” for further information.
This electronically shifted transfer case is designed to be
driven in the two-wheel drive position (2WD) for normal
street and highway conditions on dry, hard surfaced roads.
When additional traction is required, the transfer case 4WD
LOCK and 4WD LOW positions can be used to maximize
torque to the front driveshaft, forcing the front and rear
wheels to rotate at the same speed. This is accomplished by
rotating the 4WD Control Switch to the desired position.
Refer to “Shifting Procedure” in this section for specific
shifting instructions.
The 4WD LOCK and 4WD LOW positions are designed for
loose, slippery road surfaces only. Driving in the 4WD
LOCK and 4WD LOW positions on dry hard surfaced
roads may cause increased tire wear and damage to the
driveline components.
NOTE: The transfer case NEUTRAL button is located on
the lower left hand corner of the 4WD Control Switch. The transfer case NEUTRAL position is to be used for recre-
ational towing only. Refer to “Recreational Towing” in
“Starting And Operating” for further information.
Transfer Case Position Indicator Lights
The Transfer Case Position Indicator Lights (4WD and
4LOW) are located in the instrument cluster and indicate
the current and desired transfer case selection. When you
select a different transfer case position, the indicator lights
will do the following:
If All Of The Following Shift Conditions Are Met:
1. The current position indicator light will turn OFF.
2. The selected position indicator light will flash until the
transfer case completes the shift.
3. When the shift is complete, the indicator light for the
selected position will stop flashing and remain ON.
If One Or More Of The Following Shift Conditions Are
Not Met:
1. The indicator light for the current position will remain
ON.
2. The newly selected position indicator light will continue
to flash. 5STARTING AND OPERATING 343
When the parking brake is applied with the ignition switch
ON, the “Brake Warning Light” in the instrument cluster
will illuminate.
NOTE:
• When the parking brake is applied and the automatic
transmission is placed in gear, the “Brake Warning
Light” will flash. If vehicle speed is detected, a chime
will sound to alert the driver. Fully release the parking
brake before attempting to move the vehicle.
• This light only shows that the parking brake is applied.
It does not show the degree of brake application. When parking on a hill, it is important to turn the front
wheels toward the curb on a downhill grade and away
from the curb on an uphill grade. For vehicles equipped
with an automatic transmission, apply the parking brake
before placing the gear selector in PARK, otherwise the
load on the transmission locking mechanism may make it
difficult to move the gear selector out of PARK.
The parking brake should always be applied whenever the
driver is not in the vehicle.
WARNING!• Never leave children alone in a vehicle, or with access
to an unlocked vehicle. Allowing children to be in a
vehicle unattended is dangerous for a number of
reasons. A child or others could be seriously or fatally
injured. Children should be warned not to touch the
parking brake, brake pedal or the gear selector.
• Do not leave the key fob in or near the vehicle, or in a
location accessible to children, and do not leave the
ignition of a vehicle equipped with Keyless Enter-N-Go
in the ACC or ON/RUN mode. A child could operate
power windows, other controls, or move the vehicle. (Continued)Parking Brake Release 5STARTING AND OPERATING 351
• Park brake must be off.
• Driver door must be closed.
• The vehicle must be on a sufficient grade.
• The gear selection must match vehicle uphill direction
(i.e., vehicle facing uphill is in forward gear; vehicle
backing uphill is in REVERSE gear).
• HSA will work in REVERSE gear and all forward gears.
The system will not activate if the transmission is in
PARK or NEUTRAL. For vehicles equipped with a
manual transmission, if the clutch is pressed, HSA will
remain active.
WARNING!There may be situations where the Hill Start Assist
(HSA) will not activate and slight rolling may occur,
such as on minor hills or with a loaded vehicle, or
while pulling a trailer. HSA is not a substitute for
active driving involvement. It is always the driver ’s
responsibility to be attentive to distance to other ve-
hicles, people, and objects, and most importantly brake
operation to ensure safe operation of the vehicle under (Continued) WARNING! (Continued)all road conditions. Your complete attention is always
required while driving to maintain safe control of your
vehicle. Failure to follow these warnings can result in
a collision or serious personal injury.
Towing With HSA
HSA will also provide assistance to mitigate roll back while
towing a trailer.
WARNING!• If you use a trailer brake controller with your trailer, the
trailer brakes may be activated and deactivated with the
brake switch. If so, there may not be enough brake
pressure to hold both the vehicle and the trailer on a hill
when the brake pedal is released. In order to avoid
rolling down an incline while resuming acceleration,
manually activate the trailer brake or apply more ve-
hicle brake pressure prior to releasing the brake pedal.
• HSA is not a parking brake. Always apply the
parking brake fully when leaving your vehicle. Also,
be certain to leave the transmission in PARK. (Continued)356 STARTING AND OPERATING