
DRIVETRAIN
INDEX
page page
Automatic Transmission.................... 23
Clutch and Brake Pedal Bushings............. 22
Clutch Master Cylinder..................... 22
Drive Shafts............................. 26Front and Rear Axles...................... 24
Manual Transmission...................... 22
Rubber and Plastic Hoses/Tubing............. 26
Transfer Case (4WD Vehicles)................ 24
CLUTCH AND BRAKE PEDAL BUSHINGS
If the clutch and brake pedal mechanism squeaks,
the pivot bushings should be lubricated. Use Mopar
Multi-Purpose Lubricant, or an equivalent. Refer to
Group 5, Brakes for location of bushings.
CLUTCH MASTER CYLINDER
LEVEL INSPECTION
WARNING: DO NOT ALLOW PETROLEUM OR WA-
TER BASE LIQUIDS TO CONTAMINATE CLUTCH
FLUID, SEAL DAMAGE AND CLUTCH FAILURE CAN
RESULT.
The clutch reservoir level should be inspected when
other underhood service is performed. (Fig. 1)
The fluid level is determined by its height in rela-
tion to the level indicator ring (Fig. 2) located inside
the reservoir. Add fluid until the height is level with
the indicator ring.
FLUID SPECIFICATION
Use Mopar, Brake And Hydraulic Clutch Fluid or
equivalent. Use only brake fluid conforming to DOT
3, Federal, Department of Transportation specifica-
tion. To avoid fluid contamination, use fluid from a
properly sealed container.CAUTION: Never use reclaimed brake fluid or fluid
from an unsealed container. In addition, do not use
fluid from a container that has been opened and al-
lowed to stand for an extended length of time.
Moisture in the air can be absorbed by the fluid,
which causes dilution with loss of effectiveness.
MANUAL TRANSMISSION
The manual transmission should be inspected for
oil leaks and proper oil level when other under vehi-
cle service is performed.
LUBRICANT SPECIFICATION
When it becomes necessary to add to or change the
lube oil in a Jeep manual transmission, use SAE
75W-90, API Quality Grade GL-5 gear lubricant.
LUBRICANT LEVEL
The fill-hole plug for all manual transmissions is
located on the right side of the case (Fig. 3). Deter-
mine the lubricant level according to the following
procedure.
(1) Remove the fill-hole plug (Fig. 3) from the
transmission. The lube oil should be level with the
bottom edge of the fill hole. The level can be slightly
below the bottom edge of the fill hole if the lube oil is
cold.
Fig. 1 Clutch Reservoir LocationÐTypical
Fig. 2 Hydraulic Clutch Fluid LevelÐTypical
0 - 22 LUBRICATION AND MAINTENANCEJ

If the transmission is warm, lube oil could
drip out of the fill hole. This is acceptable but
the lube oil should not gush out of the fill hole.
(2) If not acceptable, raise the lube oil level to the
bottom edge of the transmission fill hole.
Add lube oil in small amounts to raise the
level.
(3) Install the fill-hole plug in the transmission.
Tighten the plug with 37 Nzm (27 ft. lbs.) torque.
LUBE OIL CHANGE
When it becomes necessary to change manual
transmission lube oil, use the following procedure.
(1) Raise and support the vehicle.
(2) Remove the fill-hole plug from the transmis-
sion.
(3) Place a container to collect the lube oil under
the transmission drain-hole plug.
(4) Remove the drain-hole plug and drain the lube
oil from the transmission into the container.
Care should be exercised when disposing
used lube oil after it has been drained from a
transmission.
(5) Install the drain-hole plug in the transmission.
Tighten the plug with 37 Nzm (27 ft. lbs.) torque.
(6) Fill the transmission until the lube oil begins to
drip out of the fill hole.
(7) Install the fill-hole plug in the transmission.
Tighten the plug with 37 Nzm (27 ft. lbs.) torque.
(8) Remove the support and lower the vehicle.
AUTOMATIC TRANSMISSION
The automatic transmission fluid should be
changed and bands adjusted at the intervals de-
scribed in the Maintenance Schedules section of this
Group. The automatic transmission should be in-
spected for fluid leaks and proper fluid level whenother under hood service is performed. Refer to
Group 21, Transmission for proper service proce-
dures.
CAUTION: To minimize fluid contamination, verify
that dipstick is seated in the fill tube after fluid level
reading is taken.
TO INSPECT THE TRANSMISSION FLUID
LEVEL
WARNING: USE EXTREME CAUTION WHEN THE
ENGINE IS OPERATING. DO NOT PUT YOUR
HANDS NEAR THE DRIVE BELT, PULLEYS OR FAN
BLADE. DO NOT STAND IN A DIRECT LINE WITH
THE FAN BLADE.
(1) Be sure transmission fluid is at normal operat-
ing temperature. Normal operating temperature is
reached after approximately 15 miles (25km) of oper-
ation.
(2) Position the vehicle on a level surface. This is
important for an accurate fluid level check.
(3) While sitting in driver seat, apply brakes and
place gear selector in each position, then move the
selector to:
²XJ vehicles-P (Park).
²YJ vehicles-N (Neutral).
(4) Apply parking brake.
(5) Raise hood and wipe off dipstick handle to pre-
vent dirt from entering fill tube. Then remove trans-
mission fluid level indicator (dipstick) and wipe clean
with a wiping cloth.
(6) Install dipstick and verify it is seated in fill
hole or tube.
(7) Remove dipstick, with handle above tip, take
fluid level reading. If the vehicle has been driven for
at least 15 minutes before inspecting fluid level,
transmission can be considered hot and reading
should be in the OK area. If vehicle has run for less
than 15 minutes and more than 60 seconds transmis-
sion can be considered warm and reading should be
above MIN mark. Add fluid only if level is below
MIN mark on dipstick when transmission is warm
(Fig. 4).
CAUTION: Do not overfill automatic transmission,
leakage or damage can result.
AUTOMATIC TRANSMISSION FLUID
SPECIFICATION
When it becomes necessary to add fluid or when
the ATF is replaced, use:
²MOPAR Dexron IIE/Mercon ATFonlyfor AW-4
automatic transmissions (XJ vehicles).
²MOPAR ATF PLUS type 7176 (YJ vehicles).
Fig. 3 Manual Transmission Fill- & Drain-Hole
PlugsÐTypical
JLUBRICATION AND MAINTENANCE 0 - 23

CLUTCH DIAGNOSIS
INDEX
page page
Clutch Contamination....................... 3
Clutch Cover and Disc Runout................ 3
Clutch Housing Misalignment................. 4
Clutch Misalignment........................ 3Flywheel Runout........................... 3
General Diagnosis Information................ 3
Inspection and Diagnosis Charts............... 4
Installation Methods and Parts Usage........... 4
GENERAL DIAGNOSIS INFORMATION
Unless the cause of a clutch problem is obvious, ac-
curate problem diagnosis will usually require a road
test to confirm a problem. Component inspection will
then be required to determine the actual problem
cause.
During a road test, drive the vehicle at normal
speeds. Shift the transmission through all gear
ranges and observe clutch action. If chatter, grab,
slip, or improper release is experienced, remove and
inspect the clutch components. However, if the prob-
lem is noise or hard shifting, further diagnosis may
be needed as the transmission or another driveline
component may be at fault. Careful observation dur-
ing the test will help narrow the problem area.
CLUTCH CONTAMINATION
Fluid contamination is a frequent cause of clutch
malfunctions. Oil, water, or clutch fluid on the clutch
disc and pressure plate surfaces will cause chatter,
slip and grab.
During inspection, note if any components are con-
taminated with oil, hydraulic fluid, or water/road
splash.
Oil contamination indicates a leak at either the
rear main seal or transmission input shaft. Oil leak-
age produces a residue of oil on the housing interior
and on the clutch cover and flywheel. Heat buildup
caused by slippage between the cover, disc and fly-
wheel, can sometimes bake the oil residue onto the
components. The glaze-like residue ranges in color
from amber to black.
Road splash contamination means dirt/water is en-
tering the clutch housing due to loose bolts, housing
cracks, or through hydraulic line openings. Driving
through deep water puddles can force water/road
splash into the housing through such openings.
Clutch fluid leaks are usually from damaged slave
cylinder push rod seals. This type of leak can only be
confirmed by visual inspection.
CLUTCH MISALIGNMENT
Clutch components must be in proper alignment
with the crankshaft and transmission input shaft.Misalignment caused by excessive runout or warpage
of any clutch component will cause grab, chatter and
improper clutch release.
FLYWHEEL RUNOUT
Check flywheel runout whenever misalignment is
suspected. Flywheel runout should not exceed 0.08
mm (0.003 in.). Measure runout at the outer edge of
the flywheel face with a dial indicator. Mount the in-
dicator on a stud installed in place of one of the fly-
wheel bolts.
Common causes of runout are:
²heat warpage
²improper machining
²incorrect bolt tightening
²improper seating on crankshaft flange shoulder
²foreign material on crankshaft flange
Flywheel machining is not recommended. The fly-
wheel clutch surface is machined to a unique contour
and machining will negate this feature. However, mi-
nor flywheel scoring can be cleaned up by hand with
180 grit emery, or with surface grinding equipment.
Remove only enough material to reduce scoring (ap-
proximately 0.001 - 0.003 in.). Heavy stock removal
isnot recommended.Replace the flywheel if scor-
ing is severe and deeper than 0.076 mm (0.003 in.).
Excessive stock removal can result in flywheel crack-
ing or warpage after installation; it can also weaken
the flywheel and interfere with proper clutch release.
Clean the crankshaft flange before mounting the
flywheel. Dirt and grease on the flange surface may
cock the flywheel causing excessive runout. Use new
bolts when remounting a flywheel and secure the
bolts with Mopar Lock And Seal. Tighten flywheel
bolts to specified torque only. Overtightening can dis-
tort the flywheel hub causing runout.
CLUTCH COVER AND DISC RUNOUT
Check the clutch disc before installation. Axial
(face) runout of anewdisc should not exceed 0.50
mm (0.020 in.). Measure runout about 6 mm (1/4 in.)
from the outer edge of the disc facing. Obtain an-
other disc if runout is excessive.
Check condition of the clutch before installation. A
warped cover or diaphragm spring will cause grab
and incomplete release or engagement. Be careful
JCLUTCH DIAGNOSIS 6 - 3

COOLING SYSTEM
CONTENTS
page page
DIAGNOSIS............................. 4
ENGINE ACCESSORY DRIVE BELTS......... 38
ENGINE BLOCK HEATER.................. 44GENERAL INFORMATION.................. 1
SERVICE PROCEDURES.................. 13
SPECIFICATIONS........................ 45
GENERAL INFORMATION
Throughout this group, references are made to par-
ticular vehicle models by alphabetical designation
(XJ or YJ) or by the particular vehicle nameplate. A
chart showing a breakdown of alphabetical designa-
tions is included in the Introduction section at the
beginning of this manual.
COOLING SYSTEM
The cooling system regulates engine operating tem-
perature. It allows the engine to reach normal oper-
ating temperature as quickly as possible, maintains
normal operating temperature and prevents over-
heating.
The cooling system also provides a means of heat-
ing the passenger compartment and cooling the auto-
matic transmission fluid (if equipped). The cooling
system is pressurized and uses a centrifugal water
pump to circulate coolant throughout the system.
An optional factory installed heavy duty cooling
package is available on most models. The package
consists of a radiator that has an increased number
of cooling fins. XJ models equipped with a 4.0L 6-cyl-inder engine and heavy duty cooling and/or air con-
ditioning also have an auxiliary electric cooling fan.
COOLING SYSTEM COMPONENTS
The cooling system consists of:
²A radiator
²Cooling fan (mechanical and/or electrical)
²Thermal viscous fan drive
²Fan shroud
²Radiator pressure cap
²Thermostat
²Coolant reserve/overflow system
²Transmission oil cooler (if equipped with an auto-
matic transmission)
²Coolant
²Water pump
²Hoses and hose clamps
SYSTEM COOLANT ROUTING
For cooling system flow routings, refer to Figs. 1, 2,
3or4.
JCOOLING SYSTEM 7 - 1

SERVICE PROCEDURES
INDEX
page page
Auxiliary Electric Cooling FanÐXJ Models with 4.0L
6-Cylinder Engine....................... 35
Coolant................................. 20
Coolant Reserve/Overflow System............. 24
Cooling System Cleaning/Reverse Flushing...... 22
Cooling System Fans...................... 32
Cooling System Hoses..................... 32
Draining Cooling System.................... 21
Radiator Pressure Cap..................... 25
Radiators............................... 26Refilling Cooling System.................... 21
Testing Cooling System for Leaks............. 22
Thermostat.............................. 17
Transmission Oil Coolers.................... 36
Viscous Fan Drive......................... 34
Water Pump Tests......................... 13
Water PumpsÐGeneral Information............ 13
Water PumpsÐRemoval/Installation........... 14
WATER PUMPSÐGENERAL INFORMATION
A centrifugal water pump circulates coolant
through the water jackets, passages, intake manifold,
radiator core, cooling system hoses and heater core.
The pump is driven from the engine crankshaft by a
drive belt on all engines.
The water pump impeller is pressed onto the rear
of a shaft that rotates in bearings pressed into the
housing. The housing has a small hole to allow seep-
age to escape. The water pump seals are lubricated
by the antifreeze in the coolant mixture. No addi-
tional lubrication is necessary.
CAUTION: All engines are equipped with a reverse
(counter-clockwise) rotating water pump and vis-
cous fan drive assembly. REVERSE is stamped or
imprinted on the cover of the viscous fan drive and
inner side of the fan. The letter R is stamped into
the back of the water pump impeller (Fig. 1).
Engines from previous model years, depending
upon application, may have been equipped with a for-
ward (clockwise) rotating water pump. Installation of
the wrong water pump will cause engine overheating.
A quick test to determine if the pump is working is
to check if the heater warms properly. A defective wa-
ter pump will not be able to circulate heated coolant
through the long heater hose to the heater core.
WATER PUMP TESTS
LOOSE IMPELLER
DO NOT WASTE reusable coolant. If solution is
clean, drain coolant into a clean container for reuse.
WARNING: DO NOT REMOVE THE CYLINDER
BLOCK DRAIN PLUGS OR LOOSEN THE RADIATOR
DRAINCOCK WITH THE SYSTEM HOT AND UNDER
PRESSURE. SERIOUS BURNS FROM THE COOL-
ANT CAN OCCUR.(1) Drain the cooling system.
(2) Loosen the fan belt(s).
(3) Disconnect the lower radiator hose from the
water pump.
(4) Bend a stiff clothes hanger or welding rod as
shown in (Fig. 2).
(5) Position the rod in the water pump inlet and
attempt to hold the impeller while turning the fan
blades. If equipped with a viscous fan drive, turn the
water pump shaft with a breaker bar and socket at-
tached to a mounting flange nut. If the impeller is
loose and can be held with the rod while the fan
blades are turning, the pump is defective. If the im-
peller turns, the pump is OK.
Connect the hose and install the coolant, or proceed
with repairs.
Fig. 1 Reverse Rotating Water PumpÐTypical
JCOOLING SYSTEM SERVICE PROCEDURES 7 - 13

WARNING: HOT, PRESSURIZED COOLANT CAN
CAUSE INJURY BY SCALDING.
Carefully remove the radiator pressure cap from
the filler neck and check the coolant level. Push
down on the cap to disengage it from the stop tabs.
Wipe the inner part of the filler neck and examine
the lower inside sealing seat for nicks, cracks, paint,
dirt and solder residue. Inspect the reserve/overflow
tank tube for internal obstructions. Insert a wire
through the tube to be sure it is not obstructed.
Inspect the cams on the outside part of the filler
neck. If the cams are bent, seating of pressure cap
valve and tester seal will be affected. Replace cap if
cams are bent.
Attach pressure tester 7700 (or an equivalent) to
the radiator filler neck (Fig. 21).Operate the tester pump to apply 124 kPa (18 psi)
pressure to the system. If the hoses enlarge exces-
sively or bulge while testing, replace as necessary.
Observe the gauge pointer and determine the condi-
tion of the cooling system according to the following
criteria:
²Holds Steady: If the pointer remains steady for
two minutes, there are no serious coolant leaks in
the system. However, there could be an internal leak
that does not appear with normal system test pres-
sure. Inspect for interior leakage or do the Internal
Leakage Test. Do this if it is certain that coolant is
being lost and no leaks can be detected.
²Drops Slowly: Shows a small leak or seepage is oc-
curring. Examine all connections for seepage or slight
leakage with a flashlight. Inspect the radiator, hoses,
gasket edges and heater. Seal any small leak holes
with a Sealer Lubricant or equivalent. Repair leak
holes and reinspect the system with pressure ap-
plied.
²Drops Quickly: Shows that a serious leakage is oc-
curring. Examine the system for serious external
leakage. If no leaks are visible, inspect for internal
leakage. Large radiator leak holes should be repaired
by a reputable radiator repair shop.
INTERNAL LEAKAGE INSPECTION
Remove the engine oil pan drain plug and drain a
small amount of engine oil. Coolant, being heavier
than engine oil, will drain first. Another way of test-
ing is to operate the engine and check for water glob-
ules on the engine oil dipstick. Also inspect the
automatic transmission oil dipstick for water glob-
ules. Inspect the automatic transmission fluid cooler
for leakage. Operate the engine without the pressure
cap on the radiator until thermostat opens.
Attach a pressure tester to the filler neck. If pres-
sure builds up quickly, a leak exists as a result of a
faulty cylinder head gasket or crack in the engine.
Repair as necessary.
WARNING: DO NOT ALLOW PRESSURE TO EX-
CEED 124 KPA (18 PSI). TURN THE ENGINE OFF.
TO RELEASE THE PRESSURE, ROCK THE TESTER
FROM SIDE TO SIDE. WHEN REMOVING THE
TESTER, DO NOT TURN THE TESTER MORE THAN
1/2 TURN IF THE SYSTEM IS UNDER PRESSURE.
If there is no immediate pressure increase, pump
the pressure tester until the indicated pressure is
within the system range. Vibration of the gauge
pointer indicates compression or combustion leakage
into the cooling system.
WARNING: DO NOT DISCONNECT THE SPARK
PLUG WIRES WHILE THE ENGINE IS OPERATING.
Fig. 20 Leak Detection Using Black LightÐTypical
Fig. 21 Pressurizing SystemÐTypical
JCOOLING SYSTEM SERVICE PROCEDURES 7 - 23

nostic Procedures manual for diagnostic information
and operation of the DRB scan tool.
To test operation of the fan relay only, refer to Re-
laysÐOperation/Testing. This can be found in Group
14, Fuel Systems.
REMOVAL
The auxiliary cooling fan is attached to the radia-
tor upper crossmember behind the radiator.
(1) Remove the two fan mounting bolts from radi-
ator upper crossmember (Fig. 43).
(2) Disconnect the electric fan connector.
(3) Lift fan straight up and out of vehicle.
INSTALLATION
(1) Align lower retaining tabs of fan shroud with
slots in bracket at bottom of radiator. Push fan down
into position.
(2) Tighten the mounting bolts to 4 Nzm (31 in.
lbs.) torque.
(3) Connect auxiliary cooling fan electrical connec-
tor.
TRANSMISSION OIL COOLERS
WATER-TO-OIL COOLER
All models equipped with an automatic transmis-
sion are equipped with a transmission oil cooler
mounted internally within the radiator tank. This in-
ternal cooler is supplied as standard equipment on
all models equipped with an automatic transmission.
Transmission oil is cooled when it passes through
this separate cooler. In case of a leak in the internalradiator mounted transmission oil cooler, engine cool-
ant may become mixed with transmission fluid or
transmission fluid may enter engine cooling system.
Both cooling system and transmission should be
drained and inspected if the internal radiator
mounted transmission cooler is leaking.
Also refer to the section on Transmission Air-to-Oil
Coolers. This auxiliary air-to-oil cooler is an option
on most engine packages.
REPLACING WATER-TO-OIL COOLER IN
RADIATOR SIDE TANK
The internal transmission oil cooler located within
the radiator is not serviceable. If it requires service,
the radiator must be replaced.
Once the repaired or replacement radiator has
been installed, fill the cooling system and inspect for
leaks. Refer to the Refilling Cooling System and Test-
ing Cooling System For Leaks sections in this group.
If the transmission operates properly after repairing
the leak, drain the transmission and remove the
transmission oil pan. Inspect for sludge and/or rust.
Inspect for a dirty or plugged inlet filter. If none of
these conditions are found, the transmission and
torque convertor may not require reconditioning. Re-
fer to Group 21 for automatic transmission servicing.
AIR-TO-OIL COOLER
An auxiliary air-to-oil transmission oil cooler is
available with most engine packages.
On XJ and YJ models, the cooler is located in front
of the radiator or A/C condenser (if equipped) and be-
hind the grill (Figs. 44, 45 or 46). It is mounted to
the front frame crossmember.
Fig. 43 Auxiliary Cooling FanÐRemove/InstallÐ
Typical
Fig. 44 Auxiliary Air-To-Oil CoolerÐYJ Models
7 - 36 COOLING SYSTEM SERVICE PROCEDURESJ

The auxiliary oil coolers on all models operate in
conjunction with the internal radiator mounted main
oil cooler. The transmission oil is routed through the
main cooler first, then the auxiliary cooler, before re-
turning to the transmission.REMOVAL/INSTALLATIONÐXJ MODELS
(1) Remove the grill mounting screws and remove
the grill. Refer to Group 23, Body for procedures.
(2) Place a drain pan below the transmission oil
cooler.
(3) Remove the two hose clamps at oil cooler inlet
and outlet tubes (Figs. 45 or 46).
(4) Remove the two oil cooler mounting bolts (Figs.
45 or 46).
(5) Remove the oil cooler from vehicle.
(6) Reverse the preceding operation for installa-
tion. Tighten the two clamps 2 Nzm (15 in. lbs.)
torque. Tighten mounting bolts to 8 Nzm (72 in. lbs.)
torque.
REMOVAL/INSTALLATIONÐYJ MODELS
(1) Remove fan shroud and radiator. Refer to the
Radiators section for procedures.
(2) Remove the air conditioning filter/drier mount-
ing bolts.
WARNING: BEFORE PROCEEDING WITH THE NEXT
STEP, BE SURE TO WEAR SAFETY GLASSES. THE
A/C SYSTEM IS UNDER PRESSURE EVEN WITH
THE ENGINE OFF.
(3) Remove the A/C condenser mounting bolts (Fig.
47).
(4) Carefully tilt the A/C condenser rearward for
access to the auxiliary transmission oil cooler.
(5) Place a drain pan below the oil cooler.
(6) Remove the two hose clamps at oil cooler inlet
and outlet tubes (Fig. 44).
(7) Remove the three oil cooler mounting bolts
(Fig. 44).
(8) Remove the oil cooler from vehicle.
(9) Reverse the preceding operation for installa-
tion. Tighten the two clamps 2 Nzm (15 in. lbs.)
torque. Tighten mounting bolts to 8 Nzm (72 in. lbs.)
torque.
Fig. 45 Auxiliary Air-To-Oil CoolerÐXJ ModelsÐ4.0L
Engine
Fig. 46 Auxiliary Air-To-Oil CoolerÐXJ ModelsÐ2.5L
Engine
Fig. 47 Condenser Mounting BoltsÐYJ Models
JCOOLING SYSTEM SERVICE PROCEDURES 7 - 37