Page 471 of 546

•Do not change the thermostat for Summer or Winter
operation. If replacement is ever necessary, install
ONLY the correct type thermostat. Other designs may
result in unsatisfactory engine coolant (antifreeze)
performance, poor gas mileage, and increased emis-
sions.
Brake System
In order to assure brake system performance, all brake
system components should be inspected periodically.
Refer to the “Maintenance Schedule” for the proper
maintenance intervals.
WARNING!
Riding the brakes can lead to brake failure and
possibly a collision. Driving with your foot resting or
riding on the brake pedal can result in abnormally
(Continued)
WARNING! (Continued)
high brake temperatures, excessive lining wear, and
possible brake damage. You would not have your full
braking capacity in an emergency.
Brake Fluid Level Check
The fluid level of the master cylinder should be checked
when performing under the hood service or immediately
if the brake system warning lamp indicates system
failure.
The brake master cylinder has a translucent plastic
reservoir. On the outboard side of the reservoir, there is a
“MAX” dot and an “MIN” dot. The fluid level must be
kept within these two dots. Do not add fluid above the
MAX mark because leakage may occur at the cap.
7
MAINTAINING YOUR VEHICLE 469
Page 473 of 546

WARNING!(Continued)
•To avoid contamination from foreign matter or
moisture, use only new brake fluid or fluid that has
been in a tightly closed container. Keep the master
cylinder reservoir cap secured at all times. Brake
fluid in a open container absorbs moisture from the
air resulting in a lower boiling point. This may
cause it to boil unexpectedly during hard or pro-
longed braking, resulting in sudden brake failure.
This could result in a collision.
• Overfilling the brake fluid reservoir can result in
spilling brake fluid on hot engine parts, causing
the brake fluid to catch fire. Brake fluid can also
damage painted and vinyl surfaces, care should be
taken to avoid its contact with these surfaces.
(Continued)
WARNING! (Continued)
•Do not allow petroleum based fluid to contaminate
the brake fluid. Brake seal components could be
damaged, causing partial or complete brake failure.
This could result in a collision.
Rear Axle And 4x4 Front Driving Axle Fluid Level
For models with 9.25 in Front Axles and 11.5 in Rear
Axles, refer to “Fluids, Lubricants, and Genuine Parts” in
“Maintaining Your Vehicle” for further information. For
normal service, periodic fluid level checks are not re-
quired. When the vehicle is serviced for other reasons,
the exterior surfaces of the axle assembly should be
inspected.
When checking the fluid level (4500/5500 only), the
vehicle should be in a level position. The fluid level
should be ¼ in±¼in(6.4 mm ± 6.4 mm) below the fill
7
MAINTAINING YOUR VEHICLE 471
Page 475 of 546

Lubricant Selection
Refer to “Fluids, Lubricants, and Genuine Parts” in
“Maintaining Your Vehicle” for further information.
NOTE:The presence of water in the gear lubricant will
result in corrosion and possible failure of differential
components. Operation of the vehicle in water, as may be
encountered in some off-highway types of service, will
require draining and refilling the axle to avoid damage.
Limited-Slip Differentials DO NOT REQUIRE any
limited slip oil additive (friction modifiers).
NOTE: Slight noise and mild shuddering may be evi-
dent while turning a vehicle with limited slip differential
on concrete or dry pavement. These conditions should be
considered normal operation of the limited slip differen-
tial.
Transfer Case
Drain And Refill
Refer to the “Maintenance Schedule” for the proper
maintenance intervals.
Lubricant Selection
Refer to “Fluids, Lubricants, and Genuine Parts” in
“Maintaining Your Vehicle” for further information.
Fluid Level Check
This fluid level can be checked by removing the filler
plug. The fluid level should be to the bottom edge of the
filler plug hole with the vehicle in a level position.
7
MAINTAINING YOUR VEHICLE 473
Page 477 of 546

CAUTION!
Do not use chemical flushes in your transmission as
the chemicals can damage your transmission compo-
nents. Such damage is not covered by the New
Vehicle Limited Warranty.
Fluid Level Check
Check the fluid level when the engine is fully warmed up
and the transmission fluid is at normal operating tem-
perature. Driving with an improper fluid level will
greatly reduce the life of the transmission and of the
fluid. Check the fluid level whenever the vehicle is
serviced.
Fluid Level Check — Procedure
It is best to check the fluid level when the transmission is
at normal operating temperature (170-180°F / 77-82°C for
66RFE transmission, or 158–176°F / 70–80°C for AS66RCtransmission). This normally occurs after at least 15 miles
(25 km) of driving. At normal operating temperature the
fluid cannot be held comfortably between the fingertips.
You can read the transmission sump temperature in the
EVIC display (see Electronic Vehicle Information Center
[EVIC] for further information).
Use the following procedure to check the transmission
fluid level properly:
1. Monitor the transmission temperature using the EVIC
display, and operate the vehicle as required to reach
the normal operating temperature.
2. Park the vehicle on level ground.
3. Run the engine at normal idle speed for at least 60 seconds, and leave the engine running for the rest of
this procedure.
4. Fully apply the parking brake and press the brake.
7
MAINTAINING YOUR VEHICLE 475
Page 478 of 546

5. Place the shift lever momentarily into each gear posi-tion (allowing time for the transmission to fully en-
gage in each position), ending with the transmission in
PARK.
6. Wipe the area around the dipstick clean to prevent dirt from entering the transmission.
7. Remove the dipstick, wipe it clean and reinsert it until seated.
8. Remove the dipstick again and note the fluid level on both sides. The fluid level reading is only valid if there
is a solid coating of oil on both sides of the dipstick.
Note that the holes in the dipstick will be full of fluid
if the actual level is at or above the hole. The fluid level
should be between the “HOT” (upper) reference holes
on the dipstick at normal operating temperature. If the
fluid level is low, add fluid through the dipstick tube
to bring it to the proper level. Do not overfill.UseONLY the recommended fluid (see
Fluids, Lubri-
cants, and Genuine Parts for fluid specifications).
After adding any quantity of oil through the dipstick
tube, wait a minimum of two minutes for the oil to
fully drain into the transmission before rechecking the
fluid level.
NOTE: If it is necessary to check the transmission below
the operating temperature, the fluid level should be
between the two “COLD” (lower) holes on the dipstick
with the fluid at 60-70°F / 16-21°C for 66RFE transmis-
sion, or 68-86°F / 20-30°C for AS66RC transmission. Only
use the COLD region of the dipstick as a rough reference
when setting the fluid level after a transmission service
or fluid change. Re-check the fluid level, and adjust as
required, once the transmission reaches normal operating
temperature.
476 MAINTAINING YOUR VEHICLE
Page 486 of 546
FUSES
WARNING!
•When replacing a blown fuse, always use an ap-
propriate replacement fuse with the same amp
rating as the original fuse. Never replace a fuse
with another fuse of higher amp rating. Never
replace a blown fuse with metal wires or any other
material. Failure to use proper fuses may result in
serious personal injury, fire and/or property dam-
age.
(Continued)
WARNING! (Continued)
•Before replacing a fuse, make sure that the ignition
is off and that all the other services are switched off
and/or disengaged.
• If the replaced fuse blows again, contact an autho-
rized dealer.
• If a general protection fuse for safety systems (air
bag system, braking system), power unit systems
(engine system, gearbox system) or steering system
blows, contact an authorized dealer.
484 MAINTAINING YOUR VEHICLE
Page 496 of 546

CAUTION!
•When installing the power distribution center
cover, it is important to ensure the cover is properly
positioned and fully latched. Failure to do so may
allow water to get into the power distribution
center and possibly result in an electrical system
failure.
• When replacing a blown fuse, it is important to use
only a fuse having the correct amperage rating. The
use of a fuse with a rating other than indicated may
result in a dangerous electrical system overload. If
a properly rated fuse continues to blow, it indicates
a problem in the circuit that must be corrected.
VEHICLE STORAGE
If you are storing your vehicle for more than 21 days, we
recommend that you take the following steps to mini-
mize the drain on your vehicle’s battery:
• Disconnect the negative cable from battery.
• Any time you store your vehicle or keep it out of
service (i.e., vacation) for two weeks or more, run the
air conditioning system at idle for about five minutes
in the fresh air and high blower setting. This will
ensure adequate system lubrication to minimize the
possibility of compressor damage when the system is
started again.
494 MAINTAINING YOUR VEHICLE
Page 497 of 546
REPLACEMENT BULBS
All of the inside bulbs are brass or glass-wedge base.
Aluminum base bulbs are not approved.
LIGHT BULBS — Interior
Bulb Number
Overhead Console Lamps TS 212-2
Dome Lamp 7679
For lighted switches, see your authorized dealer for replacement instructions.
LIGHT BULBS — Exterior
Bulb Number
Quad Headlamp – Low Beam H11
Quad Headlamp – High Beam 9005
Quad Headlamp – Front Turn Signal Lamp 3157NA
Premium Headlamp – Low Beam HIR2
Premium Headlamp – High Beam 9005
Premium Headlamp –
Front Turn Signal Lamp LED (See authorized
dealer for service)
Horizontal Fog Lamp 9145
Vertical Fog Lamp 9006
Cab Roof Marker Lamps 194NA
7
MAINTAINING YOUR VEHICLE 495