2004 SUBARU IMPREZA WRX differential

7-19
Starting and operating
– CONTINUED –
suit driving and road-surface conditions. When the ig-
nition switch is turned ON, the “AUTO” indicator light
in the combination meter comes on. The system can
be switched to a manual mode. !Manual mode
The manual mode allows the driver to set the differen-
tial-action limiting factor of the center differential as
desired to suit driving and road-surface conditions.
When this mode is selected, the “AUTO” indicator light
in the combination meter goes off. ! Manual switch
Press the “DCCD-MANU” switch on the center con- sole to switch from auto mode to manual mode. The
indicator light in the switch will come on, and the “AU-
TO” indicator light in the combination meter will go off.
Press the switch again to go back to auto mode; the in-
dicator light in the switch will go off, and the “AUTO” in-
dicator light in the combination meter will come on. !
Center differential control dial and indicator
light
The control dial is located beside the parking-brake le-
ver. By turning the control dial forward and rearward,
it is possible to change the differential-action limiting
factor of the center differential.
The center-differential indicator lights in the combina-
MANU
UG7024BA
UG7025AA

7-20
Starting and operating
tion meter give six levels of indication. The indicator
lights and control dial are linked; when the dial is
turned to change the differential-action limiting factor
(front/rear torque-distribution ratio), the illumination
position of the indicator lights change accordingly.
Turn the dial forward to increase the differential-action
limiting factor. If the white line on the dial reaches the
frontmost position, the center differential will be almost
completely locked and the “LOCK” indicator light will come on.
Turn the dial rearward to reduce the differential-action
limiting factor. If the white line on the dial reaches the
rearmost position, the factor will be minimal and the
“ ” indicator light will come on.
"
Do not turn the control dial when a wheel slip-
page occurs. Wait until the wheelspin has been
brought under control or select the auto mode." When the vehicle has been fitted with a tem-
porary spare tire or is to be towed, turn the con-
trol dial fully rearward (to minimize the differen-
tial-action limiting factor) or select the auto
UG7027BA
UG7026BA

7-21
Starting and operating
– CONTINUED –
mode.
NOTE "If the differential-limiting factor is large during
cornering maneuvers, a small speed difference
between the front and rear wheels may cause tight
corner braking (a phenomenon accompanied by
vibration and noise). This phenomenon does not
indicate a problem. It will disappear if the differen-
tial-action limiting factor is reduced. " Use the center-differential indicator light only as
a rough indication of the differential-action limit-
ing factor. ! Temporary release
When the driver stop the vehicle and pulls the parking-
brake lever after manually setting the differential-ac-
tion limiting factor, the factor is temporarily minimized.
The indicator in the combination meter continues to
show the driver’s selected differential-action limiting
factor. When the driver releases the parking-brake le-
ver, the factor set by the driver is restored.
Automatic transmission
The automatic transmission is electronically controlled
with 4-forward speeds and 1-reverse speed.
NOTE
Immediately after a disconnected battery is recon-
nected or ATF (automatic transmission fluid) is re-
placed, you may feel that the automatic transmis-
sion operation is somewhat unusual.
This results from erasure or invalidation of data
the on-board computer has collected and stored in
memory to allow the transmission to shift at the
most appropriate times for the current condition
of your vehicle. Optimized shifting will be restored
as the vehicle continues to be driven for a while.
Do not shift from the “P” or “N” position into
the “D”, “3”, “2”, “1” or “R” position while de-
pressing the accelerator pedal. This may cause
the vehicle to jump forward or backward.
" Shift into the “P” or “R” position only after

7-27
Starting and operating
– CONTINUED –
4. Insert the screwdriver into the hole.
5. Push down on the screwdriver and move the selec-
tor lever from the “P” to the “N” position.
6. Remove the screwdriver from the hole. Depress
the brake pedal and start the engine.
Take your vehicle to the nearest SUBARU dealer im-
mediately to have the system repaired. Limited slip differential (LSD) (if
equipped)
The LSD provides optimum distribution of power ac-
cording to the difference in revolutions between the
right and left wheels that may be caused by certain
driving conditions, thereby improving driving stability
on snow-covered, muddy or other slippery roads or
when high speed driving.
"
Never start the engine while a tire on one side
is jacked up, as the vehicle may move. " If one tire is spinning in mud, avoid continued
spinning at high speed as this could adversely
affect the LSD." If you use a temporary spare tire to replace a
flat tire, be sure to use the original temporary
spare tire stored in the vehicle. Using other siz-
es will adversely affect the LSD.
HS7011BA

8-29
Driving tips
– CONTINUED –
Trailer towing
Your car is designed and intended to be used primarily
as a passenger-carrying vehicle. Towing a trailer puts
additional loads on your car’s engine, drivetrain,
brakes, tires and suspension and has an adverse ef-
fect on fuel economy.
If you do decide to tow a trailer, your safety and satis-
faction depend upon proper use of correct equipment
and cautious operation of your vehicle. Seek the ad-
vice of your SUBARU dealer to assist you in purchas-
ing a hitch and other necessary towing equipment ap-
propriate for your vehicle. In addition, be sure to follow
the instructions on correct installation and use provid-
ed by the trailer and other towing equipment manufac-
turers.
SUBARU assumes no responsibility for injuries or ve-
hicle damage that result from trailer towing equipment,
or from any errors or omissions in the instructions ac-
companying such equipment or for your failure to fol-
low the proper instructions. !Warranties and maintenance
SUBARU warranties do not apply to vehicle damage
or malfunction caused by trailer towing. If you use your
vehicle to tow a trailer, more frequent maintenance will
be required due to the additional load. (Refer to “Main- tenance schedule under severe driving conditions” in
the “Warranty and Maintenance Booklet”.)
Under no circumstances should a trailer be towed with
a new vehicle or a vehicle with any new powertrain
component (engine, transmission, differential, wheel
bearings, etc.) for the first 1,000 miles (1,600 km) of
driving. !
Maximum load limits
Never exceed the maximum load limits ex-
plained below. Exceeding the maximum load
limits could cause personal injury and/or vehi-
cle damage.
"Adequate size trailer brakes are required
when the trailer and its cargo exceed 1,000 lbs
(453 kg) total weight." Before towing a trailer, check the trailer total
weight, GVW, GAWs and tongue load. Make
sure the load and its distribution in your vehicle

9-18
In case of emergency
terioration of the center differential.
! Towing and tie-down hooks
The towing hooks should be used only in an emergen-
cy (e.g., to free a stuck vehicle from mud, sand or
snow).
Front towing hook:
1. Take out the towing hook, screwdriver and wheel
nut wrench from the on board tool bag.
2. Insert a flat-head screwdriver into the slot at point A
on the front passenger side fog light cover, then use it
to pry the cover upward. The tabs at point A on the fog light cover will come free of the bumper.
3. Pull the entire fog light cover toward you.
4. Screw the towing hook into the threaded hole until
its thread becomes invisible.
5. Tighten the towing hook securely using the wheel
nut wrench.
After towing, remove the towing hook from the vehicle
and stow it in the tool bag.
Fit the fog light cover on the bumper.
"
Do not use the towing hook except when tow-
ing your vehicle.
A
UG9030BB
UG9526BA

9-21
In case of emergency
– CONTINUED –
!Towing with all wheels on the ground
1. Check the transmission and differential oil levels
and add oil to bring it to the upper level if necessary.
2. Release the parking brake and put the transmis-
sion in neutral.
3. The ignition switch should be in the “ACC” position
while the vehicle is being towed.
4. Take up slack in the towline slowly to prevent dam-
age to the vehicle.
" Never turn the ignition switch to the “LOCK”
position while the vehicle is being towed be- cause the steering wheel and the direction of
the wheels will be locked. "
Remember that the brake booster and power
steering do not function when the engine is not
running. Because the engine is turned off, it will
take greater effort to operate the brake pedal
and steering wheel.
" If transmission failure occurs, transport your
vehicle on a flat-bed truck. " Do not run the engine while being towed us-
ing this method. Transmission damage could
result if the vehicle is towed with the engine
running. " For vehicles with automatic transmission,
the traveling speed must be limited to less than
20 mph (30 km/h) and the traveling distance to
less than 31 miles (50 km). For greater speeds
and distances, transport your vehicle on a flat-
bed truck.
HG9024AA

11 - 1
11
Maintenance and service
Maintenance schedule ................................. 11-3
Maintenance precautions ............................ 11-3 Before checking or servicing in the engine compartment .................................................. 11-4
When you do checking or servicing in the engine compartment while the engine is
running ............................................................ 11-5
Engine hood .................................................. 11-5
Engine compartment overview ................... 11-8 2.5 liter model .................................................... 11-8
2.0 liter (Turbo) model ...................................... 11-9
2.5 liter (Turbo) model ...................................... 11-10
Engine oil ...................................................... 11-11 Checking the oil level ....................................... 11-11
Changing the oil and oil filter .......................... 11-12
Recommended grade and viscosity ................ 11-16
Recommended grade and viscosity under severe driving conditions .............................. 11-18
Synthetic oil ....................................................... 11-18
Cooling system ............................................. 11-18 Cooling fan, hose and connections ................ 11-19
Engine coolant .................................................. 11-19
Air cleaner element ...................................... 11-23 Replacing the air cleaner element ................... 11-23
Spark plugs ................................................... 11-26 Recommended spark plugs ............................. 11-27
Drive belts ..................................................... 11-27
Manual transmission oil ............................... 11-28 Checking the oil level ....................................... 11-28
Recommended grade and viscosity ................ 11-30 Automatic transmission fluid ...................... 11-31
Checking the fluid level .................................... 11-31
Recommended fluid ......................................... 11-32
Front differential gear oil (AT vehicles) ...... 11-33 Checking the oil level ....................................... 11-33
Recommended grade and viscosity ............... 11-33
Rear differential gear oil ............................... 11-34 Checking the gear oil level .............................. 11-34
Recommended grade and viscosity ............... 11-35
Power steering fluid ...................................... 11-36 Checking the fluid level .................................... 11-36
Recommended fluid ......................................... 11-37
Brake fluid ..................................................... 11-37 Checking the fluid level .................................... 11-37
Recommended brake fluid ............................... 11-38
Clutch fluid (MT vehicles) ............................ 11-38 Checking the fluid level .................................... 11-38
Recommended clutch fluid .............................. 11-39
Brake booster ................................................ 11-40
Brake pedal .................................................... 11-40 Checking the brake pedal free play ................ 11-40
Checking the brake pedal reserve distance ... 11-41
Clutch pedal (MT vehicles) ........................... 11-41 Checking the clutch function .......................... 11-41
Checking the clutch pedal free play ............... 11-42
Replacement of brake pad and lining ......... 11-42 Breaking-in of new brake pads and linings .... 11-43
Parking brake stroke .................................... 11-44
Tires and wheels ........................................... 11-44