2002 JEEP GRAND CHEROKEE Transfer

SPECIFICATIONS
TORQUE SPECIFICATIONS
DESCRIPTION N´m Ft. Lbs. In. Lbs.
Front Shaft - Companion Flange Bolts 32 24 -
4.7L Front Shaft - Axle Yoke Nuts 19 14 -
4.7L Front Shaft - Transfer Case Bolts 27 20 -
Rear Shaft - Yoke Nuts 19 14 -
SPECIAL TOOLS
Fig. 7 U-JOINT ANGLE EXAMPLE
1 - 4.9É Angle (C)
2 - 3.2É Angle (B)
3 - Input Yoke4 - 3.0É Angle (A)
5 - Output Yoke
Inclinometer 7663
WJPROPELLER SHAFT 3 - 5
PROPELLER SHAFT (Continued)

PROPELLER SHAFT - FRONT
REMOVAL
NOTE: Different length propeller shafts are used for
different drivetrain applications. Ensure that the
correct propeller shaft is used.
(1) Place vehicle on floor or drive-on hoist with full
weight of vehicle on suspension.
(2) Shift the transmission and transfer case, if nec-
essary, into the Neutral position.
(3) Measure the distance from the face of the C/V
joint cup to the end of the C/V joint boot (Fig. 8).
(4) The correct length is 142.7 mm (5.61 in.).
NOTE: If the measurement is not correct, the wrong
shaft may have been installed or a mating compo-
nent (front axle or transfer case) may be installed
incorrectly. Investigate and correct as necessary.
(5) Mark a line across the companion flange at the
transfer case and C/V joint at the rear of the front
propeller shaft for installation reference.
(6) Mark a line across the C/V joints and the pin-
ion companion flanges for installation reference.
(7) Remove bolts from the front C/V joint to the
pinion companion flange.
(8) Remove bolts from the rear C/V joint to the
transfer case companion flange.
(9) Push the propeller shaft forward to clear trans-
fer case companion flange and remove the shaft.
INSTALLATION
NOTE: Different length propeller shafts are used for
different drivetrain applications. Ensure that the
correct propeller shaft is used.
(1) Install the shaft between companion flanges.
(2) The shaft should rotate freely in the pinion
flange.
(3) Align marks on the companion flanges with the
marks on the C/V joints.
(4) Install bolts to the front C/V joint and tighten
bolts to 32 N´m (24 ft. lbs.).
(5) Install the bolts to the rear C/V joint and
tighten bolts to 32 N´m (24 ft. lbs.).
(6) Verify propeller shaft length.
(7) Lower vehicle.
PROPELLER SHAFT - FRONT
4.7L
REMOVAL
(1) Raise and support vehicle.
(2) Remove crossmember/skid plate as necessary to
gain access to the propeller shaft.
(3) Shift transmission and transfer case, if neces-
sary into Neutral.
(4) Mark a line across the yoke at the transfer
case, link yoke and propeller shaft yoke at the rear of
the front propeller shaft for installation reference
(Fig. 9).
(5) Mark a line across the propeller shaft yoke and
pinion shaft yoke for installation reference.
Fig. 8 MEASUREMENT
1 - C/V JOINT CUP
2 - C/V BOOT END
3 - MEASUREMENT
Fig. 9 REFERENCE MARKS ON YOKES
1 - REFERENCE MARKS
3 - 6 PROPELLER SHAFTWJ

(6) Remove the U-joint strap bolts at the pinion
shaft yoke (Fig. 10).
(7) Remove bolts holding rear universal joint to
the transfer case yoke.
(8) Separate the rear universal joint from the
transfer case yoke.
(9) Push rear of propeller shaft upward to clear
transfer case yoke.
(10) Separate front universal joint from front axle.
(11) Separate propeller shaft from vehicle.
INSTALLATION
(1) Position front propeller shaft under vehicle
with rear universal joint over the transfer case yoke.
(2) Place front universal joint into the axle pinion
yoke.
(3) Align mark on the rear link yoke and universal
joint to the mark on the transfer case yoke.
(4) Loosely install bolts to hold universal joint to
transfer case yoke.
(5) Align mark on front universal joint to the mark
on the axle pinion yoke.
(6) Tighten the U-joint strap/clamp bolts at the
axle yoke to 19 N´m (14 ft. lbs.).
(7) Tighten the universal joint to transfer case
bolts to 27 N´m (20 ft. lbs.).
(8) Lower the vehicle.
PROPELLER SHAFT - REAR
REMOVAL
(1) Raise and support vehicle on safety stands.
(2) Shift the transmission and transfer case if nec-
essary, to their neutral positions.
(3) Mark a line across the axle pinion yoke and the
propeller shaft yoke for installation reference.
(4) Remove the bolts holding the universal joint
clamps to the pinion yoke.
(5) Slide the slip yoke off of the transmission, or
transfer case, output shaft and remove the propeller
shaft (Fig. 11).
INSTALLATION
(1) Slide the slip yoke on the transmission, or
transfer case, output shaft.
(2) Align the installation reference marks made on
the propeller shaft and pinion yoke.
(3) Position universal joint into pinion yoke.
(4) Install the universal joint clamp and clamp
bolts to the pinion yoke. Tighten bolts to 19 N´m (14
ft. lbs.).
(5) Lower the vehicle.
Fig. 10 FRONT PROPELLER SHAFT - 4.7L
1 - FRONT AXLE
2 - BOOT
3 - PROPELLER SHAFT
4 - DOUBLE CARDAN U-JOINT
5 - TRANSFER CASE
6 - BOOT
7 - SLINGER
8 - CLAMP
9 - YOKE
Fig. 11 REAR PROPELLER SHAFT
1 - SLIDING YOKE
2 - PROPELLER SHAFT
3 - PINION YOKE
4 - CLAMP/STRAP
5 - BOLT
6 - OUTPUT SHAFT
WJPROPELLER SHAFT 3 - 7
PROPELLER SHAFT - FRONT 4.7L (Continued)

FRONT AXLE - 186FBI
TABLE OF CONTENTS
page page
FRONT AXLE - 186FBI
DESCRIPTION.........................15
OPERATION...........................15
DIAGNOSIS AND TESTING................16
REMOVAL.............................20
INSTALLATION.........................21
ADJUSTMENTS........................21
SPECIFICATIONS.......................30
SPECIAL TOOLS.......................31
AXLE SHAFTS
REMOVAL.............................34
INSTALLATION.........................34
AXLE SHAFT SEALS
REMOVAL.............................35
INSTALLATION.........................35
AXLE - C/V JOINT
REMOVAL.............................35
INSTALLATION.........................35
AXLE - U-JOINT
REMOVAL.............................36INSTALLATION.........................37
PINION SEAL
REMOVAL.............................37
INSTALLATION.........................37
COLLAPSIBLE SPACER
REMOVAL.............................39
INSTALLATION.........................39
DIFFERENTIAL
REMOVAL.............................40
DISASSEMBLY.........................42
ASSEMBLY............................42
INSTALLATION.........................43
DIFFERENTIAL CASE BEARINGS
REMOVAL.............................44
INSTALLATION.........................44
PINION GEAR/RING GEAR
REMOVAL.............................45
INSTALLATION.........................46
FRONT AXLE - 186FBI
DESCRIPTION
The Front Beam-design Iron (FBI) axle consists of
a cast iron differential housing with axle shaft tubes
extending from either side. The tubes are pressed
into the differential housing and welded. The axles
are semi-floating axle shafts, meaning the loads are
supported by the hub bearings. The axle shafts are
retained by nuts at the hub bearings.
The differential case is a one-piece design. Differ-
ential bearing preload and ring gear backlash is
adjusted by the use of shims located between the dif-
ferential bearing cups and housing. Pinion bearing
preload is set and maintained by the use of a collaps-
ible spacer. A differential cover provides a means for
inspection and servicing.
An optional Vari-Loktdifferential has a one-piece
differential case which contains the gerotor pump
assembly and the clutch mechinism. This unit is ser-
viced as an assembly.
OPERATION
The axle receives power from the transfer case
through the front propeller shaft. The front propeller
shaft is connected to the pinion gear which rotatesthe differential through the gear mesh with the ring
gear bolted to the differential case. The engine power
is transmitted to the axle shafts through the pinion
mate and side gears. The side gears are splined to
the axle shafts.
STANDARD DIFFERENTIAL
During straight-ahead driving, the differential pinion
gears do not rotate on the pinion mate shaft. This
occurs because input torque applied to the gears is
divided and distributed equally between the two side
gears. As a result, the pinion gears revolve with the pin-
ion mate shaft but do not rotate around it (Fig. 1).
When turning corners, the outside wheel must
travel a greater distance than the inside wheel to
complete a turn. The difference must be compensated
for to prevent the tires from scuffing and skidding
through turns. To accomplish this, the differential
allows the axle shafts to turn at unequal speeds (Fig.
2). In this instance, the input torque applied to the
pinion gears is not divided equally. The pinion gears
now rotate around the pinion mate shaft in opposite
directions. This allows the side gear and axle shaft
attached to the outside wheel to rotate at a faster
speed.
WJFRONT AXLE - 186FBI 3 - 15

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)

BEARING NOISE
The axle shaft, differential and pinion bearings can
all produce noise when worn or damaged. Bearing
noise can be either a whining or a growling sound.
Pinion bearings have a constant-pitch noise. This
noise changes only with vehicle speed. Pinion bearing
noise will be higher pitched because it rotates at a
faster rate. Drive the vehicle and load the differen-
tial. If bearing noise occurs, the rear pinion bearing
is the source of the noise. If the bearing noise is
heard during a coast, the front pinion bearing is the
source.
Worn or damaged differential bearings usually pro-
duce a low pitch noise. Differential bearing noise is
similar to pinion bearing noise. The pitch of differen-
tial bearing noise is also constant and varies only
with vehicle speed.
Axle shaft bearings produce noise and vibration
when worn or damaged. The noise generally changes
when the bearings are loaded. Road test the vehicle.
Turn the vehicle sharply to the left and to the right.
This will load the bearings and change the noise
level. Where axle bearing damage is slight, the noise
is usually not noticeable at speeds above 30 mph.
LOW SPEED KNOCK
Low speed knock is generally caused by a worn
U-joint or by worn side-gear thrust washers. A worn
pinion shaft bore will also cause low speed knock.
VIBRATION
Vibration at the rear of the vehicle is usually
caused by a:
²Damaged drive shaft.
²Missing drive shaft balance weight(s).²Worn or out-of-balance wheels.
²Loose wheel lug nuts.
²Worn U-joint(s).
²Loose/broken springs.
²Damaged axle shaft bearing(s).
²Loose pinion gear nut.
²Excessive pinion yoke run out.
²Bent axle shaft(s).
Check for loose or damaged front±end components
or engine/transmission mounts. These components
can contribute to what appears to be a rear-end
vibration. Do not overlook engine accessories, brack-
ets and drive belts.
All driveline components should be examined
before starting any repair.
(Refer to 22 - TIRES/WHEELS - DIAGNOSIS AND
TESTING)
DRIVELINE SNAP
A snap or clunk noise when the vehicle is shifted
into gear (or the clutch engaged), can be caused by:
²High engine idle speed.
²Transmission shift operation.
²Loose engine/transmission/transfer case mounts.
²Worn U-joints.
²Loose spring mounts.
²Loose pinion gear nut and yoke.
²Excessive ring gear backlash.
²Excessive side gear to case clearance.
The source of a snap or a clunk noise can be deter-
mined with the assistance of a helper. Raise the vehi-
cle on a hoist with the wheels free to rotate. Instruct
the helper to shift the transmission into gear. Listen
for the noise, a mechanics stethoscope is helpful in
isolating the source of a noise.
WJFRONT AXLE - 186FBI 3 - 17
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)

(33) Push and hold ring gear upward while not
allowing the pinion gear to rotate.
(34) Zero dial indicator face to pointer.
(35) Push and hold ring gear downward while not
allowing the pinion gear to rotate. Dial indicator
reading should be between 0.12 mm (0.005 in.) and
0.20 mm (0.008 in.). If backlash is not within specifi-
cations transfer the necessary amount of shim thick-
ness from one side of the housing to the other (Fig.
20).
(36) Verify differential case and ring gear runout
by measuring ring to pinion gear backlash at eight
locations around the ring gear. Readings should not
vary more than 0.05 mm (0.002 in.). If readings vary
more than specified, the ring gear or the differential
case is defective.
After the proper backlash is achieved, perform
Gear Contact Pattern Analysis procedure.
GEAR CONTACT PATTERN
The ring gear and pinion teeth contact patterns
will show if the pinion depth is correct in the hous-
ing. It will also show if the ring gear backlash has
been adjusted correctly. The backlash can be adjusted
within specifications to achieve desired tooth contact
patterns.
(1) Apply a thin coat of hydrated ferric oxide or
equivalent to the drive and coast side of the ring gear
teeth.
(2) Wrap, twist and hold a shop towel around the
pinion yoke to increase the turning resistance of the
pinion. This will provide a more distinct contact pat-
tern.
(3) With a boxed end wrench on a ring gear bolt,
rotate the differential case one complete revolution inboth directions while a load is being applied from
shop towel.
The areas on the ring gear teeth with the greatest
degree of contact against the pinion teeth will squee-
gee the compound to the areas with the least amount
of contact. Note and compare patterns on the ring
gear teeth to Gear Tooth Contact Patterns chart (Fig.
21)and adjust pinion depth and gear backlash as nec-
essary.
Fig. 20 BACKLASH SHIM ADJUSTMENT
3 - 28 FRONT AXLE - 186FBIWJ
FRONT AXLE - 186FBI (Continued)