2002 JEEP GRAND CHEROKEE Time

METRIC SYSTEM
DESCRIPTION
The metric system is based on quantities of one,
ten, one hundred, one thousand and one million.The following chart will assist in converting metric
units to equivalent English and SAE units, or vise
versa.
CONVERSION FORMULAS AND EQUIVALENT VALUES
MULTIPLY BY TO GET MULTIPLY BY TO GET
in-lbs x 0.11298 = Newton Meters
(N´m)N´m x 8.851 = in-lbs
ft-lbs x 1.3558 = Newton Meters
(N´m)N´m x 0.7376 = ft-lbs
Inches Hg (60É F) x 3.377 = Kilopascals (kPa) kPa x 0.2961 = Inches Hg
psi x 6.895 = Kilopascals (kPa) kPa x 0.145 = psi
Inches x 25.4 = Millimeters (mm) mm x 0.03937 = Inches
Feet x 0.3048 = Meters (M) M x 3.281 = Feet
Yards x 0.9144 = Meters M x 1.0936 = Yards
mph x 1.6093 = Kilometers/Hr.
(Km/h)Km/h x 0.6214 = mph
Feet/Sec x 0.3048 = Meters/Sec (M/S) M/S x 3.281 = Feet/Sec
mph x 0.4470 = Meters/Sec (M/S) M/S x 2.237 = mph
Kilometers/Hr. (Km/h) x 0.27778 = Meters/Sec (M/S) M/S x 3.600 Kilometers/Hr. (Km/h)
COMMON METRIC EQUIVALENTS
1 inch = 25 Millimeters 1 Cubic Inch = 16 Cubic Centimeters
1 Foot = 0.3 Meter 1 Cubic Foot = 0.03 Cubic Meter
1 Yard = 0.9 Meter 1 Cubic Yard = 0.8 Cubic Meter
1 Mile = 1.6 Kilometers
Refer to the Metric Conversion Chart to convert
torque values listed in metric Newton- meters (N´m).
Also, use the chart to convert between millimeters
(mm) and inches (in.) (Fig. 4).
WJINTRODUCTION 5

WHEEL ALIGNMENT
TABLE OF CONTENTS
page page
WHEEL ALIGNMENT
DESCRIPTION..........................3
OPERATION............................3
STANDARD PROCEDURE
STANDARD PROCEDURE - CAMBER.......3STANDARD PROCEDURE - CASTER.......4
STANDARD PROCEDURE - TOE POSITION . . 4
SPECIFICATIONS
ALIGNMENT..........................5
WHEEL ALIGNMENT
DESCRIPTION
Wheel alignment involves the correct positioning of
the wheels in relation to the vehicle. The positioning
is accomplished through suspension and steering
linkage adjustments. An alignment is considered
essential for efficient steering, good directional stabil-
ity and to minimize tire wear. The most important
measurements of an alignment are caster, camber
and toe position (Fig. 1).
CAUTION: Never attempt to modify suspension or
steering components by heating or bending.
CAUTION: Components attached with a nut and cot-
ter pin must be torqued to specification. Then if the
slot in the nut does not line up with the cotter pin
hole, tighten nut until it is aligned. Never loosen the
nut to align the cotter pin hole.
NOTE: Periodic lubrication of the front suspension/
steering system components may be required. Rub-
ber bushings must never be lubricated, Refer to
Lubrication And Maintenance for the recommended
maintenance schedule.
OPERATION
²CASTERis the forward or rearward tilt of the
steering knuckle from vertical. Tilting the top of the
knuckle rearward provides positive caster. Tilting the
top of the knuckle forward provides negative caster.
Caster is a directional stability angle. This angle
enables the front wheels to return to a straight
ahead position after turns (Fig. 1).
²CAMBERis the inward or outward tilt of the
wheel relative to the center of the vehicle. Tilting the
top of the wheel inward provides negative camber.
Tilting the top of the wheel outward provides positive
camber. Incorrect camber will cause wear on theinside or outside edge of the tire. The angle is not
adjustable, damaged component(s) must be replaced
to correct the camber angle (Fig. 1).
²WHEEL TOE POSITIONis the difference
between the leading inside edges and trailing inside
edges of the front tires. Incorrect wheel toe position
is the most common cause of unstable steering and
uneven tire wear. The wheel toe position is thefinal
front wheel alignment adjustment (Fig. 1).
²STEERING AXIS INCLINATION ANGLEis
measured in degrees and is the angle that the steer-
ing knuckles are tilted. The inclination angle has a
fixed relationship with the camber angle. It will not
change except when a spindle or ball stud is dam-
aged or bent. The angle is not adjustable, damaged
component(s) must be replaced to correct the steering
axis inclination angle.
²THRUST ANGLEis the angle of the rear axle
relative to the centerline of the vehicle. Incorrect
thrust angle can cause off-center steering and exces-
sive tire wear. This angle is not adjustable, damaged
component(s) must be replaced to correct the thrust
angle (Fig. 1).
STANDARD PROCEDURE
STANDARD PROCEDURE - CAMBER
Before each alignment reading the vehicle should
be jounced (rear first, then front). Grasp each
bumper at the center and jounce the vehicle up and
down three times. Always release the bumper in the
down position.
To obtain an accurate alignment, a 4 wheel align-
ment machine must be used and the equipment cali-
bration verified.
The wheel camber angle is preset. This angle is not
adjustable and cannot be altered.
WJWHEEL ALIGNMENT 2 - 3

STANDARD PROCEDURE - CASTER
Before each alignment reading the vehicle should
be jounced (rear first, then front). Grasp each
bumper at the center and jounce the vehicle up and
down three times. Always release the bumper in the
down position.
To obtain an accurate alignment, a 4 wheel align-
ment machine must be used and the equipment cali-
bration verified.
The wheel caster angle is preset. This angle is not
adjustable and cannot be altered.
STANDARD PROCEDURE - TOE POSITION
Before each alignment reading the vehicle should
be jounced (rear first, then front). Grasp each
bumper at the center and jounce the vehicle up and
down three times. Always release the bumper in the
down position.To obtain an accurate alignment, a 4 wheel align-
ment machine must be used and the equipment cali-
bration verified.
NOTE: For an accurate wheel toe position adjust-
ment the engine must be engine running.
(1) Apply parking brakes.
(2) Start the engine and turn wheels both ways
before straightening the steering wheel. Center and
secure the steering wheel.
(3) Loosen the tie rod adjustment sleeve clamp
bolts (Fig. 2).
(4) Turn the sleeve to obtain the preferred positive
TOE-IN specification. Position the clamp bolts as
shown (Fig. 2) for proper clearance.
(5) Tighten the clamp bolts to 68 N´m (50 ft. lbs.).
Fig. 1 Wheel Alignment Measurements
1 - WHEEL CENTERLINE
2 - NEGATIVE CAMBER ANGLE
3 - PIVOT CENTERLINE
4 - SCRUB RADIUS
5 - TRUE VERTICAL6 - KING PIN
7 - VERTICAL
8 - POSITIVE CASTER
2 - 4 WHEEL ALIGNMENTWJ
WHEEL ALIGNMENT (Continued)

VARI-LOKTDIFFERENTIAL
In a standard differential if one wheel spins, the
opposite wheel will generate only as much torque as
the spinning wheel.
A gerotor pump and clutch pack are used to pro-
vide the torque transfer capability. One axle shaft is
splined to the gerotor pump and one of the differen-
tial side gears, which provides the input to the pump.
As a wheel begins to lose traction, the speed differ-
ential is transmitted from one side of the differential
to the other through the side gears. The motion of
one side gear relative to the other turns the inner
rotor of the pump. Since the outer rotor of the pump
is grounded to the differential case, the inner and
outer rotors are now moving relative to each other
and therefore creates pressure in the pump. The tun-ing of the front and rear axle orifices and valves
inside the gerotor pump is unique and each system
includes a torque-limiting pressure relief valve to
protect the clutch pack, which also facilitates vehicle
control under extreme side-to-side traction varia-
tions. The resulting pressure is applied to the clutch
pack and the transfer of torque is completed.
Under conditions in which opposite wheels are on
surfaces with widely different friction characteristics,
Vari-loktdelivers far more torque to the wheel on
the higher traction surface than do conventional
Trac-loktsystems. Because conventional Trac-lokt
differentials are initially pre-loaded to assure torque
transfer, normal driving (where inner and outer
wheel speeds differ during cornering, etc.) produces
torque transfer during even slight side-to-side speed
variations. Since these devices rely on friction from
this preload to transfer torque, normal use tends to
cause wear that reduces the ability of the differential
to transfer torque over time. By design, the Vari-lokt
system is less subject to wear, remaining more con-
sistent over time in its ability to transfer torque. The
coupling assembly is serviced as a unit. From a ser-
vice standpoint the coupling also benefits from using
the same lubricant supply as the ring and pinion
gears.
DIAGNOSIS AND TESTING
GEAR NOISE
Axle gear noise can be caused by insufficient lubri-
cant, incorrect backlash, tooth contact, worn/damaged
gears or the carrier housing not having the proper
offset and squareness.
Gear noise usually happens at a specific speed
range. The noise can also occur during a specific type
of driving condition. These conditions are accelera-
tion, deceleration, coast or constant load.
When road testing, first warm-up the axle fluid by
driving the vehicle at least 5 miles and then acceler-
ate the vehicle to the speed range where the noise is
the greatest. Shift out-of-gear and coast through the
peak-noise range. If the noise stops or changes
greatly:
²Check for insufficient lubricant.
²Incorrect ring gear backlash.
²Gear damage.
Differential side gears and pinions can be checked
by turning the vehicle. They usually do not cause
noise during straight-ahead driving when the gears
are unloaded. The side gears are loaded during vehi-
cle turns. A worn pinion mate shaft can also cause a
snapping or a knocking noise.
Fig. 1 DIFFERENTIAL-STRAIGHT AHEAD DRIVING
1 - IN STRAIGHT AHEAD DRIVING EACH WHEEL ROTATES AT
100% OF CASE SPEED
2 - PINION GEAR
3 - SIDE GEAR
4 - PINION GEARS ROTATE WITH CASE
Fig. 2 DIFFERENTIAL-ON TURNS
1 - PINION GEARS ROTATE ON PINION SHAFT
3 - 16 FRONT AXLE - 186FBIWJ
FRONT AXLE - 186FBI (Continued)

Condition Possible Causes Correction
Axle Noise 1. Insufficient lubricant. 1. Fill differential with the correct
fluid type and quantity.
2. Improper ring gear and pinion
adjustment.2. Check ring gear and pinion
contact pattern.
3. Unmatched ring gear and pinion. 3. Replace gears with a matched
ring gear and pinion.
4. Worn teeth on ring gear and/or
pinion.4. Replace ring gear and pinion.
5. Loose pinion bearings. 5. Adjust pinion bearing pre-load.
6. Loose differential bearings. 6. Adjust differential bearing
pre-load.
7. Mis-aligned or sprung ring gear. 7. Measure ring gear run-out.
Replace components as necessary.
8. Loose differential bearing cap
bolts.8. Inspect differential components
and replace as necessary. Ensure
that the bearing caps are torqued
tot he proper specification.
9. Housing not machined properly. 9. Replace housing.
VARI-LOKT
(1) Park the vehicle on a level surface or raise
vehicle on hoist so that the vehicle is level.
(2) Remove the axle fill plug.
(3) Verify that the axle fluid level is correct. The
fluid level is correct if the fluid is level with the bot-
tom of the fill hole.
(4) Shift the transfer case into the 4WD full-time
position.
(5) Drive the vehicle in a tight circle for 2 minutes
at 5mph to fully prime the pump.
(6) Block the tires opposite the axle to be tested to
prevent the vehicle from moving.
(7) Shift the transfer case into the 4WD Low posi-
tion and the transmission into the Park position.
(8) Raise both the wheels of the axle to be tested
off of the ground.
(9) Rotate the left wheel by hand at a minimum of
one revolution per second while an assistant rotates
the right wheel in the opposite direction.
(10) The left wheel should spin freely at first and
then increase in resistance within 5 revolutions until
the wheels cannot be continuously rotated in opposite
directions.
(11) The Vari-loktdifferential has engaged prop-
erly if the wheels cannot be rotated in opposite direc-
tions for a moment. After the wheels stop rotating for
a moment, the fluid pressure will drop in the differ-
ential and the wheels begin to rotate once again.
(12) If the system does not operate properly,
replace the Vari-loktdifferential.
REMOVAL
(1) Raise and support the vehicle.
(2) Position a suitable lifting device under the
axle.
(3) Secure axle to lift.
(4) Remove the wheels and tires.
(5) Remove the brake calipers and rotors (Refer to
5 - BRAKES/HYDRAULIC/MECHANICAL/ROTORS
- REMOVAL) from the axle.
(6) Disconnect the wheel sensor wiring harness
from the vehicle wiring harness.
(7) Disconnect the vent hose from the axle shaft
tube.
(8) Mark propeller shaft and yoke/pinion flange for
installation alignment reference.
(9) Remove propeller shaft.
(10) Disconnect stabilizer bar links at the axle.
(11) Disconnect shock absorbers from axle brack-
ets.
(12) Disconnect track bar.
(13) Disconnect the tie rod and drag link from the
steering knuckle.
(14) Disconnect the steering damper from the axle
bracket.
(15) Disconnect the upper and lower suspension
arms from the axle brackets.
(16) Lower the lifting device enough to remove the
axle. The coil springs will drop with the axle.
(17) Remove the coil springs from the axle.
3 - 20 FRONT AXLE - 186FBIWJ
FRONT AXLE - 186FBI (Continued)

(21) Push and hold differential case to ring gear
side of the housing and record dial indicator reading
(Fig. 18). Add dummy shim thickness to this reading.
This will be the total shim thickness to achieve zero
backlash.
(22) Subtract 0.076 mm (0.003 in.) from the dial
indicator reading to compensate for backlash between
ring and pinion gears. This total is the thickness
shim required to achieve proper backlash.
(23) Subtract the backlash shim thickness from
the total preload shim thickness. The remainder is
the shim thickness required on the pinion side of the
axle housing.
(24) Rotate dial indicator out of the way on pilot
stud.(25) Remove differential case and dummy bearings
from the housing.
(26) Install side bearings and cups on differential
case.
(27) Install spreader W-129-B with Adapter Set
6987 on the housing and spread axle opening enough
to receive differential case.
(28) Place the bearing preload shims in the axle
housing, against the axle tubes.
(29) Install differential case into the housing.
CAUTION: When installing a Vari-LokTdifferential,
the oil feed tube must point to the bottom of the
housing. If differential is forced in with the oil feed
towards the top, the anti-rotation tabs will be dam-
aged.
(30) Remove spreader from the housing.
(31) Rotate the differential case several times to
seat the side bearings.
(32) Position the indicator plunger against a ring
gear tooth (Fig. 19).
Fig. 18 RECORED DIAL INDICATOR READING
1 - DIAL INDICATOR
2 - DIFFERENTIAL CASE TO RING GEAR SIDE
3 - PINION GEAR
4 - DIFFERENTIAL HOUSING
5 - DIFFERENTIAL CASE
Fig. 19 RING GEAR BACKLASH
1 - DIAL INDICATOR
WJFRONT AXLE - 186FBI 3 - 27
FRONT AXLE - 186FBI (Continued)

INSTALLATION
(1) Pack the bearing caps 1/3 full of wheel bearing
lubricant. Apply extreme pressure (EP), lithium-base
lubricant to aid in installation.
(2) Position the spider in the yoke. Insert the seals
and bearings, then tap bearing caps into the yoke
bores far enough to hold the spider in position.
(3) Place the socket (driver) against one bearing
cap. Position the yoke with the socket in a vise.
(4) Tighten the vise to force the bearing caps into
the yoke. Force the caps enough to install the retain-
ing clips.
(5) Install the bearing cap retaining clips.
(6) Install axle shaft.
PINION SEAL
REMOVAL
(1) Raise and support the vehicle.
(2) Remove wheel and tire assemblies.
(3) Remove brake rotors and calipers, refer to 5
Brakes for procedures.
(4) Mark propeller shaft and pinion companion
flange for installation reference.
(5) Remove the propeller shaft from the pinion
companion flange.
(6) Rotate the pinion gear a minimum of ten times
and verify the pinion rotates smoothly.
(7) Record torque necessary to rotate the pinion
gear with a inch pound torque wrench.
(8) Using a short piece of pipe and Spanner
Wrench 6958 to hold the pinion companion flange
and remove the pinion nut and washer.
(9) Remove pinion companion flange with Remover
C-452 and Flange Wrench C-3281.
(10) Remove pinion seal with Remover 7794-A and
a slide hammer (Fig. 31).
INSTALLATION
(1) Apply a light coating of gear lubricant on the
lip of pinion seal. Install seal with an appropriate
installer (Fig. 32).
(2) Install pinion companion flange on the pinion
gear with Installer W-162-D, Cup 8109 and Wrench
6958.
CAUTION: Never exceed the minimum tightening
torque 298 N´m (220 ft. lbs.) while installing pinion
nut at this point. Damage to collapsible spacer or
bearings may result.
(3) Install the pinion washer and anewnut on
the pinion gear.Tighten the nut only enough to
remove the shaft end play.
Fig. 29 AXLE SHAFT OUTER U-JOINT
1 - SHAFT YOKE
2 - BEARING CAP
3 - SNAP RINGS
4 - BEARING CAP
5 - SPINDLE YOKE
6 - BEARING
7 - BEARING CAP
8 - SNAP RINGS
9 - BEARING CAP
Fig. 30 YOKE BEARING CAP
1 - LARGE-DIAMETER SOCKET
2 - VISE
3 - SMALL-DIAMETER SOCKET
WJFRONT AXLE - 186FBI 3 - 37
AXLE - U-JOINT (Continued)

CAUTION: Never loosen pinion nut to decrease pin-
ion rotating torque and never exceed specified pre-
load torque. If preload torque or rotating torque is
exceeded a new collapsible spacer must be
installed.
(4) Rotate pinion a minimum of ten time and ver-
ify pinion rotates smoothly. Rotate the pinion shaft
with an inch pound torque wrench. Rotating torque
should be equal to the reading recorded during
removal plus 0.56 N´m (5 in. lbs.) (Fig. 33).
(5) If the rotating torque is low, use Spanner
Wrench 6958 to hold the pinion companion flange
(Fig. 34), and tighten the pinion shaft nut in 6.8 N´m
(5 ft. lbs.) increments until proper rotating torque is
achieved.
CAUTION: If maximum tightening torque is reached
prior to reaching the required rotating torque, thecollapsible spacer may have been damaged.
Replace the collapsible spacer.
Fig. 31 PINION SEAL
1 - REMOVER
2 - SLIDE HAMMER
3 - PINION SEAL
Fig. 32 PINION SEAL
1 - HANDLE
2 - INSTALLER
Fig. 33 PINION ROTATION TORQUE
1 - PINION YOKE/COMPANION FLANGE
2 - INCH POUND TORQUE WRENCH
Fig. 34 PINION SHAFT NUT
1 - PINION FLANGE
2 - FRONT AXLE
3 - SPANNER WRENCH
3 - 38 FRONT AXLE - 186FBIWJ
PINION SEAL (Continued)