engine JEEP WRANGLER 2008 JK / 3.G Service Manual

ENGINE BLOCK HEATER — IF EQUIPPED
The engine block heater warms engine coolant and
permits quicker starts in cold weather. Connect the cord
to a standard 110-115 Volt AC electrical outlet with a
grounded, three wire extension cord. The engine block
heater cord is found under the hood bundled in front of
the battery tray.
WARNING!
Remember to disconnect the cord before driving.
Damage to the 110-115 Volt AC electrical cord could
cause electrocution.
Use the heater when temperatures below 0°F (-18°C) are
expected to last for several days.
MANUAL TRANSMISSION
WARNING!
You or others could be injured if you leave the
vehicle unattended without having the parking
brake fully applied. The parking brake should al-
ways be applied when the driver is not in the vehicle,
especially on an incline.
CAUTION!
Never drive with your foot resting on the clutch
pedal, or attempt to hold the vehicle on a hill with the
clutch pedal partially engaged, as this will cause
abnormal wear on the clutch.
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Manual Transmission Shift Speeds in MPH (KM/H)
En-
gine Speeds 1 to 2 2 to 3 3 to 4 4 to 5 5 to 6
3.8L Accel. 15 (24) 24 (39)34
(55) 47
(76) 56
(90)
Cruise 10 (16) 19 (31)27
(43) 37
(60) 41
(66)
Downshifting
Moving from a high gear down to a lower gear is
recommended to preserve brakes when driving down
steep hills. In addition, downshifting at the right time
provides better acceleration when you desire to resume
speed. Downshift progressively. Do not skip gears to
avoid overspeeding the engine and clutch.
WARNING!
Do not downshift for additional engine braking on a
slippery surface. The drive wheels could lose their
grip and the vehicle could skid.
CAUTION!
When descending a hill, be very careful to downshift
one gear at a time to prevent overspeeding the engine
which can cause valve damage, and/or clutch disc
damage even if the clutch pedal is depressed.
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Maximum Recommended Downshift Speeds
CAUTION!
Failure to follow the maximum recommended down-
shifting speeds may cause the engine to overspeed
and/or damage the clutch disc even if the clutch pedal
is depressed.
Manual Transmission Downshift Speeds in MPH(KM/H)
Gear
Selec-
tion 6to5 5to4 4to3 3to2 2to1
Maxi-
mum
Speed 80 (129) 70 (113) 50 (81) 30 (48) 15 (24)
Reverse Shifting
To shift into REVERSE, bring the vehicle to a complete
stop. Depress the clutch and pause briefly to allow the
gear train to stop rotating. Beginning from the NEUTRAL
position, move the shift lever in one quick smooth
motion straight across and into the REVERSE area (the
driver will feel a firm “click” as the shifter passes the
“knock-over”). Complete the shift by pulling the shift
lever into REVERSE.
The “knock-over” prevents the driver from accidentally
entering the REVERSE shift area and warns the driver
that they are about to shift the transmission into RE-
VERSE. Due to this feature, a slow shift to REVERSE can
be perceived as a high shift effort.
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AUTOMATIC TRANSMISSION
CAUTION!
Damage to the transmission may occur if the follow-
ing precautions are not observed:
•Shift into PARK only after the vehicle has come to
a complete stop.
•Shift into or out of REVERSE only after the
vehicle has come to a complete stop and the engine
is at idle speed.
•Do not shift from REVERSE, PARK, or NEUTRAL
into any forward gear when the engine is above
idle speed.
•Before shifting into any gear, make sure your foot
is firmly on the brake pedal.
WARNING!
It is dangerous to move the shift lever out of PARK or
NEUTRAL if the engine speed is higher than idle
speed. If your foot is not firmly on the brake pedal,
the vehicle could accelerate quickly forward or in
reverse. You could lose control of the vehicle and hit
someone or something. Only shift into gear when the
engine is idling normally and when your foot is
firmly on the brake pedal.
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Brake/Transmission Interlock System
This system prevents you from moving the shift lever out
of PARK and into any gear unless the brake pedal is
pressed. This system is active only while the ignition
switch is in the ON position. Always depress thebrake
pedal first, before moving the shift lever out of PARK.
Automatic Transmission with Overdrive
Shifting from DRIVE to PARK or REVERSE (or from P or
R to D) should be done only after the accelerator pedal is
released and the vehicle is stopped. Be sure to keep your
foot on the brake when moving the shift lever between
these gears.
Gear Ranges
DO NOT race the engine when shifting from PARK or
NEUTRAL position into another gear range.
Automatic Shift Controls
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PARK
This gear position supplements the parking brake by
locking the transmission. The engine can be started in
this range. Never use PARK while the vehicle is in
motion. Apply the parking brake when leaving the
vehicle in this range. Always apply parking brake first,
then place the shift lever in the PARK position.
WARNING!
Never use the PARK position as a substitute for the
parking brake. Always apply parking brake fully
when parked to guard against vehicle movement and
possible injury or damage.
WARNING!
It is dangerous to move the shift lever out of PARK or
NEUTRAL if the engine speed is higher than idle
speed. If your foot is not firmly on the brake pedal,
the vehicle could accelerate quickly forward or in
reverse. You could lose control of the vehicle and hit
someone or something. Only shift into gear when the
engine is idling normally and when your right foot is
firmly on the brake pedal.
REVERSE
Use this range only after the vehicle has come to a
complete stop.
NEUTRAL
Shift into NEUTRAL when the vehicle is standing for
prolonged periods with the engine running. The engine
may be started in this range. Set the parking brake if you
must leave the vehicle.
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Overdrive can be locked out by pressing the O/D OFF
switch located on the center console. The O/D OFF
indicator light (on the switch) will illuminate to show
that the switch has been activated. When the indicator
light is on, Overdrive is locked out. Pressing the switch a
second time restores the Overdrive function. The lockout
feature is useful when towing a trailer or carrying a
heavy load.
2 (Second)
For moderate grades and to assist braking on dry pave-
ment or in mud and snow. Begins from a stop in low gear
with automatic upshift to 2nd gear. Will not shift to 3rd.
1 (First)
For hard pulling at low speeds in mud, sand, snow, or on
steep grades. Begins and stays in low gear with no
upshift. Provides engine compression braking at low
speeds.CAUTION!
•Before moving the shift lever out of PARK, you
must turn the ignition from LOCK so the steering
wheel and shift lever are released. Otherwise,
damage to steering column or shift lever could
result.
•Never race the engine with the brakes on and the
vehicle in gear, and never hold the vehicle on an
incline without applying the brakes. These prac-
tices can overheat and damage the transmission.
•When “rocking” a stuck vehicle by moving be-
tween DRIVE and REVERSE, do not spin the
wheels faster than 15 mph (24 km/h), or drivetrain
damage may result.
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rear wheels to rotate at the same speed. This is accom-
plished by simply moving the shift lever to one of these
positions. The 4H and 4L positions are intended for loose,
slippery road surfaces only, and not intended for normal
driving. Driving in the 4H and 4L positions on hard
surfaced roads will cause increased tire wear and damage
to the driveline components.
The 4WD Indicator Light (located in the instrument
cluster) alerts the driver that the vehicle is in four-wheel
drive, and the front and rear driveshafts are locked
together. The light will illuminate when the transfer case
is shifted into the 4H position.
NOTE:Do not attempt to shift when only the front or
rear wheels are spinning. The transfer case is not
equipped with a synchronizer, and the front and rear
driveshaft speeds must be equal for a shift to take place.
Shifting while only the front or rear wheels are spinning
can cause damage to the transfer case. When operating your vehicle in 4L, the engine speed will
be approximately three times (four times for Rubicon
models) that of the 2H or 4H positions at a given road
speed. Take care not to overspeed the engine.
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
cause damage to the transfer case.
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.
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Trac-Lok™ is especially helpful during slippery driving
conditions. With both rear wheels on a slippery surface, a
slight application of the accelerator will supply maxi-
mum traction.
WARNING!
On vehicles equipped with a limited-slip differen-
tial, never run the engine with one rear wheel off the
ground. The vehicle may drive through the rear
wheel remaining on the ground and cause you to lose
control of your vehicle.
AXLE LOCK (TRU–LOK™) — RUBICON MODELS
The AXLE LOCK switch is located on the lower switch
bank (below the climate controls).
This feature will only activate when the following con-
ditions are met:
•Key in ignition, vehicle in 4L (Low) range.
Axle Lock Switch
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When To Use 4L (Low) Range
When off-road driving, shift into 4L (Low) for additional
traction and control on slippery or difficult terrain,
ascending or descending steep hills, and to increase low
speed pulling power. This range should be limited to
extreme situations such as deep snow, mud, steep in-
clines, or sand where additional low speed pulling power
is needed. Vehicle speeds in excess of 25 mph (40 km/h)
should be avoided when in 4L (Low) range.
Simultaneous Brake And Throttle Operation
Many off-road driving conditions require the simulta-
neous use of the brake and throttle (two-footed driving).
When climbing rocks, logs, or other stepped objects,
using light brake pressure with light throttle will keep the
vehicle from jerking or lurching. This technique is also
used when you need to stop and restart a vehicle on a
steep incline.
Driving In Snow, Mud and Sand
Snow
In heavy snow or for additional control and traction at
slower speeds, shift the transmission into a low gear and
the transfer case into 4L (Low) if necessary. Don’t shift to
a lower gear than necessary to maintain headway. Over-
revving the engine can spin the wheels and traction will
be lost. If you start to slow to a stop, try turning your
steering wheel no more than a 1/4 turn quickly back and
forth, while still applying throttle. This will allow the
tires to get a freshbiteand help maintain your momen-
tum.
CAUTION!
On icy or slippery roads, do not downshift at high
engine RPM or vehicle speeds, because engine brak-
ing may cause skidding and loss of control.
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