Drive train JEEP GRAND CHEROKEE 2003 WJ / 2.G Workshop Manual

OPERATION
REACTION PLANETARY GEARTRAIN
The reaction planetary carrier and reverse sun
gear of the reaction planetary geartrain are a single
component which is held by the 2C clutch when
required. The reaction annulus gear is a stand alone
component that can be driven by the reverse clutch
or held by the 4C clutch. The reaction sun gear is
driven by the overdrive clutch.
REVERSE PLANETARY GEARTRAIN
The reverse planetary geartrain is the middle of
the three planetary sets. The reverse planetary car-
rier can be driven by the overdrive clutch as
required. The reverse planetary carrier is also
splined to the input annulus gear, which can be held
by the low/reverse clutch. The reverse planetary
annulus, input planetary carrier, and output shaft
are all one piece.
INPUT PLANETARY GEARTRAIN
The input sun gear of the input planetary
geartrain is driven by the underdrive clutch.
DISASSEMBLY
(1) Remove the snap-ring holding the input annu-
lus into the input carrier (Fig. 104).
(2) Remove the input annulus from the input car-
rier (Fig. 104).
(3) Remove the number 9 bearing from the reverse
planetary carrier. Note that this planetary carrier
has four pinion gears.
(4) Remove the reverse planetary gear carrier (Fig.
104).
(5) Remove the number 10 bearing from the input
sun gear (Fig. 104).
(6) Remove the input sun gear from the input car-
rier (Fig. 104).
(7) Remove the number 11 bearing from the input
carrier (Fig. 104).
CLEANING
Clean the planetary components in solvent and dry
them with compressed air.
INSPECTION
Check sun gear and driving shell condition.
Replace the gear if damaged or if the bushings are
scored or worn. The bushings are not serviceable.
Fig. 104 Reverse/Input Planetary Carrier Assembly
1 - SNAP-RING 5 - INPUT PLANETARY CARRIER
2 - BEARING NUMBER 10 6 - INPUT SUN GEAR
3 - BEARING NUMBER 11 7 - REVERSE PLANETARY CARRIER
4 - INPUT ANNULUS
21 - 260 AUTOMATIC TRANSMISSION - 545RFEWJ
PLANETARY GEARTRAIN (Continued)

Replace the driving shell if worn, cracked or dam-
aged.
Replace planetary gear sets if gears, pinion pins, or
carrier are damaged in any way. Replace the annulus
gears and supports if either component is worn or
damaged.
Replace the output shaft if the machined surfaces
are scored, pitted, or damaged in any way. Also
replace the shaft if the splines are damaged, or
exhibits cracks at any location.
ASSEMBLY
(1) Clean and inspect all components. Replace any
components which show evidence of excessive wear
or scoring.
(2) Install the number 11 bearing into the input
planetary carrier so that the inner race will be
toward the front of the transmission (Fig. 104).
(3) Install the input sun gear into the input carrier
(Fig. 104).
(4) Install the number 10 bearing onto the rear of
the reverse planetary carrier with the inner race
toward the carrier (Fig. 104).
(5) Install the number 9 bearing onto the front of
the reverse planetary carrier with the outer race
toward the carrier and the inner race facing upward
(Fig. 104).
(6) Install the reverse planetary gear carrier into
the input carrier (Fig. 104).
(7) Install the input annulus gear into the input
carrier (Fig. 104).
(8) Install the snap-ring to hold the input annulus
gear into the input carrier (Fig. 104).
SHIFT MECHANISM
DESCRIPTION
The gear shift mechanism provides six shift posi-
tions which are:
²Park (P)
²Reverse (R)
²Neutral (N)
²Drive (D)
²Manual second (2)
²Manual low (1)
OPERATION
MANUAL LOW (1) range provides FIRST gear
only. Overrun braking is also provided in this range.
MANUAL SECOND (2) range provides FIRST and
SECOND gear only.
DRIVE range provides FIRST, SECOND, THIRD
and OVERDRIVE FOURTH and FIFTH gear ranges.
The shift into OVERDRIVE FOURTH and FIFTH
gear range occurs only after the transmission hascompleted the shift into D THIRD gear range. No
further movement of the shift mechanism is required
to complete the 3-4 or 4-5 shifts.
The FOURTH and FIFTH gear upshifts occurs
automatically when the overdrive selector switch is
in the ON position. An upshift to FOURTH and
FIFTH gears may not occur or may be delayed in
some of the possible shift schedules. (Refer to 8 -
ELECTRICAL/ELECTRONIC CONTROL MOD-
ULES/TRANSMISSION CONTROL MODULE -
OPERATION)
REMOVAL
(1) Remove any necessary console parts for access
to shift lever assembly and shifter cables. (Refer to
23 - BODY/INTERIOR/FLOOR CONSOLE -
REMOVAL)
(2) Shift transmission into PARK.
(3) Disconnect the transmission shift cable at shift
lever and shifter assembly bracket (Fig. 105).
(4) Disconnect the park lock cable from the shifter
BTSI lever and the shifter assembly bracket. (Fig.
106)
(5) Disconnect the transfer case shift cable from
the transfer case shift lever pin (Fig. 107), if
equipped.
(6) Remove the clip holding the transfer case shift
cable to the shifter assembly bracket, if equipped.
(7) Remove the transfer case shift cable from the
shifter assembly bracket, if equipped.
(8) Disengage all wiring connectors from the
shifter assembly.
(9) Remove all nuts holding the shifter assembly to
the floor pan (Fig. 108).
Fig. 105 Transmission Shift Cable
1 - SHIFT LEVER PIN
2 - ADJUSTMENT SCREW
3 - SHIFT CABLE
4 - SHIFTER ASSEMBLY BRACKET
WJAUTOMATIC TRANSMISSION - 545RFE 21 - 261
PLANETARY GEARTRAIN (Continued)

TRANSFER CASE - NV242
TABLE OF CONTENTS
page page
TRANSFER CASE - NV242
DESCRIPTION........................280
OPERATION..........................281
DIAGNOSIS AND TESTING - TRANSFER
CASE - NV242.......................281
REMOVAL............................282
DISASSEMBLY........................282
CLEANING...........................292
INSPECTION.........................293
ASSEMBLY...........................295
INSTALLATION........................307
SPECIFICATIONS
TRANSFER CASE - NV242.............308
SPECIAL TOOLS
TRANSFER CASE - NV242.............308
FLUID
STANDARD PROCEDURE - FLUID DRAIN/
REFILL............................310FRONT OUTPUT SHAFT SEAL
REMOVAL............................310
INSTALLATION........................310
POSITION SENSOR
DESCRIPTION........................311
OPERATION..........................311
REMOVAL............................312
INSTALLATION........................312
REAR RETAINER BUSHING AND SEAL -
NV242HD
REMOVAL............................312
INSTALLATION........................312
SHIFT CABLE
REMOVAL............................313
INSTALLATION........................313
TRANSFER CASE - NV242
DESCRIPTION
The NV242 is a full transfer case (Fig. 1). It pro-
vides full time 2-wheel, or 4-wheel drive operation.
A differential in the transfer case is used to control
torque transfer to the front and rear axles. A low
range gear provides increased low speed torque capa-
bility for off road operation. The low range provides a
2.72:1 reduction ratio.
The geartrain is mounted in two aluminum case
halves attached with bolts. The mainshaft front and
rear bearings are mounted in aluminum retainer
housings bolted to the case halves.
TRANSFER CASE IDENTIFICATION
Two versions of the NV242 are used in the WJ
vehicles, NV242LD and NV242HD. The two transfer
cases can be distinguished from one another by the
rear output shaft retainer. The NV242LD uses a rub-
ber boot to cover the rear output shaft, while the
NV242HD uses a cast aluminum housing. Other than
this difference, the two transfer cases are serviced
the same.
A circular ID tag is attached to the rear case of
each transfer case (Fig. 2). The ID tag provides the
transfer case model number, assembly number, serial
number, and low range ratio.The transfer case serial number also represents
the date of build.
SHIFT MECHANISM
Operating ranges are selected with a lever in the
floor mounted shifter assembly. The shift lever is con-
nected to the transfer case range lever by an adjust-
able cable. A straight line shift pattern is used.
Range positions are marked on the shifter bezel.
Fig. 1 NV242 Transfer Case
21 - 280 TRANSFER CASE - NV242WJ

OPERATION
The input gear is splined to the transmission out-
put shaft. It drives the mainshaft through the plan-
etary gear and range hub. The front output shaft is
operated by a drive chain that connects the shaft to a
drive sprocket on the mainshaft. The drive sprocket
is engaged/disengaged by the mode fork, which oper-
ates the mode sleeve and hub. The sleeve and hub
are not equipped with a synchro mechanism for shift-
ing.
OPERATING RANGES
NV242 operating ranges are 2WD (2-wheel drive),
4x4 part-time, 4x4 full time, and 4 Lo.
The 2WD and 4x4 full time ranges can be used at
any time and on any road surface.
The 4x4 part-time and 4 Lo ranges are for off road
use only. The only time these ranges can be used on
hard surface roads, is when the surface is covered
with snow and ice.
DIAGNOSIS AND TESTING - TRANSFER CASE - NV242
DIAGNOSIS CHART
CONDITION POSSIBLE CAUSE CORRECTION
Transfer case difficult to shift or will
not shift into desired range.1) Transfer case shift linkage
binding.1) Repair or replace linkage as
necessary.
2) Insufficient or incorrect lubricant. 2) Drain and refill transfer case with
the correct type and quantity of
lubricant.
3) Internal transfer case
components binding, worn, or
damaged.3) Repair or replace components as
necessary.
Transfer case noisy in all drive
modes.1) Insufficient or incorrect lubricant. 1) Drain and refill transfer case with
the correct type and quantity of
lubricant.
Lubricant leaking from transfer case
seals or vent.1) Transfer case overfilled. 1) Drain lubricant to the correct
level.
2) Transfer case vent closed or
restricted.2) Clean or replace vent as
necessary.
3) Transfer case seals damaged or
installed incorrectly.3) Replace suspect seal.
Transfer case will not shift through
4X4 part time range (light remains
on)1) Incomplete shift due to drivetrain
torque load.1) Momentarily release the
accelerator pedal to complete the
shift.
2) Incorrect tire pressure. 2) Correct tire pressure as
necessary.
3) Excessive Tire wear. 3) Correct tire condition as
necessary.
4) Excessive vehicle loading. 4) Correct as necessary.
Fig. 2 Fill/Drain Plug And I.D. Tag Locations
1 - I.D. TAG
2 - FILL PLUG
3 - DRAIN PLUG
WJTRANSFER CASE - NV242 21 - 281
TRANSFER CASE - NV242 (Continued)

(2) Remove retainer (Fig. 28).
(3) Remove front tabbed thrust washer (Fig. 29).
(4) Remove input gear (Fig. 30).
(5) Remove rear tabbed thrust washer from low
range gear (Fig. 31).
CLEANING
Clean the transfer case components with parts
cleaning solvent. Flush the oil passages in the cases
and drivetrain components with solvent. This will
help remove dirt and particles from these passages.
Dry the transfer case components with compressed
air or allow them to air dry on clean shop towels.
Apply compressed air through all oil passages in
the cases and gear components to clear them of any
residue.
INSPECTION
MAINSHAFT
Examine the mainshaft components carefully for
evidence of wear or damage.
Replace the thrust washers if worn or damaged.
Replace the mainshaft and sprocket gears if the
teeth or gear bores are worn or damaged.
Replace the mainshaft bearings if worn, flat spot-
ted, brinelled, or damaged in any way.
Replace the mainshaft if it is bent, exhibits wear or
damage to the bearing surfaces, splines or gear teeth.
Fig. 28 Input Gear Retainer
1 - INPUT GEAR
2 - LOW RANGE GEAR
3 - RETAINER
Fig. 29 Front Tabbed Thrust Washer
1 - FRONT TABBED THRUST WASHER
Fig. 30 Input Gear Removal
1 - INPUT GEAR
2 - LOW RANGE GEAR
Fig. 31 Rear Tabbed Thrust Washer Removal
1 - LOW RANGE GEAR
2 - REAR TABBED THRUST WASHER
21 - 324 TRANSFER CASE - NV247WJ
TRANSFER CASE - NV247 (Continued)

INPUT AND LOW RANGE GEARS
Inspect the low range gear pinions and pinion pins.
Replace the low range gear if any of the pins or pin-
ions are worn or damaged.
Inspect the thrust washers, retainer, and snap-
ring. Replace the snap-ring if bent, or distorted.
Replace the thrust washers and retainer if worn,
cracked or damaged in any way.
Examine the input gear carefully. Be sure the gear
teeth and bearing surfaces are in good condition.
Replace the gear if wear or damage is evident.
Check the input gear pilot bearing. Rotate the
bearing and check for roughness or noise. Also check
bearing position in the bore. The bearing should be
recessed approximately 2.5 mm (0.100 in.) below the
top edge of the bore. The bearing should not be
seated at the bottom of the bore. Replace the bearing
if worn, or roughness is evident. Replace both the
gear and bearing if the bearing is a loose fit in the
bore.
GEAR CASE AND RETAINERS
Examine both case halves and retainers carefully.
Replace any retainer or case half if wear, cracks, or
other damage is evident.
Check condition of the low range annulus gear and
the shift rail bushing in the front case (Fig. 32). The
low range annulus gear is not a serviceable part.
Replace the gear and case as an assembly if the gear
is loose, worn, or damaged. The shift rail bushing is
a serviceable part and can be replaced if necessary.
Check the bushing in the rear retainer. Replace the
bushing if worn or scored.
Examine the sealing surfaces of both case halves
and retainers. Small burrs, or scratches on these sur-
faces can be reduced with crocus cloth or a fine tooth
file.
Examine condition of the shift rail bushing in the
front case. If the bushing is worn or damaged, it can
be removed with a blind hole type puller. A replace-
ment bushing can be installed with a suitable size
driver. Recess the bushing slightly below the edge of
the bore but do not seat it all the into the case.
GEARTRAIN
Inspect the mainshaft splines, gear teeth and bear-
ing surfaces carefully for evidence of wear, or dam-
age. Replace the shaft if necessary. do not attempt to
salvage it if damaged.
The shift rail and range fork are an assembly.
Replace both parts if either is damaged. However, the
nylon pads in the fork can be replaced if worn, or
cracked.
Inspect the transfer case snap-rings closely. Do not
attempt to salvage a distorted snap-ring by straight-ening or reshaping it. Replace any snap-ring that is
distorted, or worn.
Inspect the low range gear, input gear and the gear
thrust washers retainer, and snap-ring. The low
range gear is serviced as an assembly only. Replace
the gear if the case or pinions are damaged.
During inspection, also make sure the seal surface
of the input gear is in good condition. Minor nicks on
this surface can be reduced with crocus cloth. How-
ever, replace the gear if the seal surface is severely
scored or worn.
OIL PUMP AND PROGRESSIVE COUPLING
The oil pump and progressive coupling are not ser-
viceable components. Replace the coupling as an
assembly if it is damaged. Replace the oil pump as
an assembly if the gear teeth are worn, or if the
pump has become damaged.
BEARINGS AND SEALS
The transfer case seals should be replaced during
overhaul. Use new seals in the input gear bearing
retainer, front case and rear retainer. Also replace
the yoke seal washer and the detent plug O-ring.
Check condition of each transfer case bearing.
Replace any bearing exhibiting signs of roughness,
wear, or damage.
Fig. 32 Low Range Annulus Gear Location
1 - LOW RANGE ANNULUS GEAR
2 - SHIFT RAIL BUSHING
WJTRANSFER CASE - NV247 21 - 325
TRANSFER CASE - NV247 (Continued)

TIRES
DESCRIPTION
DESCRIPTION - TIRES
Tires are designed and engineered for each specific
vehicle. They provide the best overall performance
for normal operation. The ride and handling charac-
teristics match the vehicle's requirements. With
proper care they will give excellent reliability, trac-
tion, skid resistance, and tread life.
Driving habits have more effect on tire life than
any other factor. Careful drivers will obtain in most
cases, much greater mileage than severe use or care-
less drivers. A few of the driving habits which will
shorten the life of any tire are:
²Rapid acceleration
²Severe brake applications
²High speed driving
²Excessive speeds on turns
²Striking curbs and other obstacles
Radial-ply tires are more prone to irregular tread
wear. It is important to follow the tire rotation inter-
val shown in the section on Tire Rotation.(Refer to 22
- TIRES/WHEELS - STANDARD PROCEDURE),
This will help to achieve a greater tread life.
TIRE IDENTIFICATION
Tire type, size, aspect ratio and speed rating are
encoded in the letters and numbers imprinted on the
side wall of the tire. Refer to the chart to decipher
the tire identification code (Fig. 12).
Performance tires have a speed rating letter after
the aspect ratio number. The speed rating is not
always printed on the tire sidewall. These ratings
are:
²Qup to 100 mph
²Sup to 112 mph
²Tup to 118 mph
²Uup to 124 mph
²Hup to 130 mph
²Vup to 149 mph
²Zmore than 149 mph (consult the tire manu-
facturer for the specific speed rating)
An All Season type tire will have eitherM+S,M
&SorM±S(indicating mud and snow traction)
imprinted on the side wall.
TIRE CHAINS
Tire snow chains may be used oncertainmodels.
Refer to the Owner's Manual for more information.
DESCRIPTION - RADIAL±PLY TIRES
Radial-ply tires improve handling, tread life and
ride quality, and decrease rolling resistance.Radial-ply tires must always be used in sets of
four. Under no circumstances should they be used on
the front only. They may be mixed with temporary
spare tires when necessary. A maximum speed of 50
MPH is recommended while a temporary spare is in
use.
Radial-ply tires have the same load-carrying capac-
ity as other types of tires of the same size. They also
use the same recommended inflation pressures.
The use of oversized tires, either in the front or
rear of the vehicle, can cause vehicle drive train fail-
ure. This could also cause inaccurate wheel speed
signals when the vehicle is equipped with Anti-Lock
Brakes.
The use of tires from different manufactures on the
same vehicle is NOT recommended. The proper tire
pressure should be maintained on all four tires.
DESCRIPTION - TIRE INFLATION PRESSURES
Under inflation will cause rapid shoulder wear, tire
flexing, and possible tire failure (Fig. 13).
Over inflation will cause rapid center wear and
loss of the tire's ability to cushion shocks (Fig. 14).
Improper inflation can cause:
²Uneven wear patterns
²Reduced tread life
²Reduced fuel economy
Fig. 12 Tire Identification
22 - 6 TIRES/WHEELSWJ

SPARE TIRE
DESCRIPTION - SPARE / TEMPORARY TIRE
The temporary spare tire is designed for emer-
gency use only. The original tire should be repaired
or replaced at the first opportunity, then reinstalled.
Do not exceed speeds of 50 M.P.H. when using the
temporary spare tire. Refer to Owner's Manual for
complete details.
WHEELS
DESCRIPTION
The rim size is on the vehicle safety certification
label located on the drivers door shut face. The size
of the rim is determined by the drivetrain package.
Original equipment wheels/rims are designed for
operation up to the specified maximum vehicle capac-
ity.
All models use stamped steel, cast aluminum or
forged aluminum wheels. Every wheel has raised sec-
tions between the rim flanges and rim drop well
called safety humps (Fig. 18) .
Initial inflation of the tire forces the bead over
these raised sections. In case of rapid loss of air pres-
sure, the raised sections help hold the tire on the
wheel.
The wheel studs and nuts are designed for specific
applications. All aluminum and some steel wheels
have wheel stud nuts with an enlarged nose. This
enlarged nose is necessary to ensure proper retentionof the wheels. Do not use replacement studs or nuts
with a different design or lesser quality.
DIAGNOSIS AND TESTING - WHEEL
INSPECTION
Inspect wheels for:
²Excessive run out
²Dents or cracks
²Damaged wheel lug nut holes
²Air Leaks from any area or surface of the rim
NOTE: Do not attempt to repair a wheel by hammer-
ing, heating or welding.
If a wheel is damaged an original equipment
replacement wheel should be used. When obtaining
replacement wheels, they should be equivalent in
load carrying capacity. The diameter, width, offset,
pilot hole and bolt circle of the wheel should be the
same as the original wheel.
WARNING: FAILURE TO USE EQUIVALENT
REPLACEMENT WHEELS MAY ADVERSELY
AFFECT THE SAFETY AND HANDLING OF THE
VEHICLE. USED WHEELS ARE NOT RECOM-
MENDED. THE SERVICE HISTORY OF THE WHEEL
MAY HAVE INCLUDED SEVERE TREATMENT OR
VERY HIGH MILEAGE. THE RIM COULD FAIL WITH-
OUT WARNING.
STANDARD PROCEDURE - WHEEL
REPLACEMENT
The wheel studs and nuts are designed for specific
applications. They must be replaced with equivalent
parts. Do not use replacement parts of lesser quality
or a substitute design. All aluminum and some steel
wheels have wheel stud nuts which feature an
enlarged nose. This enlarged nose is necessary to
ensure proper retention of the aluminum wheels.
NOTE: Do not use chrome plated lug nuts with
chrome plated wheels.
Before installing the wheel, be sure to remove any
build up of corrosion on the wheel mounting surfaces.
Ensure wheels are installed with good metal-to-metal
contact. Improper installation could cause loosening
of wheel nuts. This could affect the safety and han-
dling of your vehicle.
To install the wheel, first position it properly on
the mounting surface. All wheel nuts should then be
tightened just snug. Gradually tighten them in
sequence to the proper torque specification.Never
use oil or grease on studs or nuts.
Wheels must be replaced if they have:
²Excessive runout
Fig. 18 Safety Rim
1 - FLANGE
2 - RIDGE
3 - WELL
22 - 10 TIRES/WHEELSWJ

A/C COMPRESSOR CLUTCH
DESCRIPTION
The compressor clutch assembly consists of a sta-
tionary electromagnetic coil, a hub bearing and pul-
ley assembly, and a clutch plate (Fig. 4). The
electromagnetic coil unit and the hub bearing and
pulley assembly are each retained on the nose of the
compressor front housing with snap rings. The clutch
plate is keyed to the compressor shaft and secured
with a bolt.
OPERATION
The compressor clutch components provide the
means to engage and disengage the compressor from
the engine serpentine accessory drive belt. When the
clutch coil is energized, it magnetically draws the
clutch into contact with the pulley and drives the
compressor shaft. When the coil is not energized, the
pulley freewheels on the clutch hub bearing, which is
part of the pulley. The compressor clutch and coil are
the only serviced parts on the compressor.
The compressor clutch engagement is controlled by
several components: the a/c switch on the a/c heater
control panel, the Automatic Zone Control (AZC) con-
trol module (if the vehicle is so equipped), the evap-
orator probe, the a/c high pressure transducer, the
a/c compressor clutch relay, the body control module
(BCM) and the Powertrain Control Module (PCM).
The PCM may delay compressor clutch engagement
for up to thirty seconds. Refer to Electronic Control
Modules for more information on the PCM controls.
DIAGNOSIS AND TESTING - COMPRESSOR
CLUTCH COIL
For circuit descriptions and diagrams, refer to the
appropriate wiring diagrams. The battery must be
fully-charged before performing the following tests.
Refer to Battery for more information.
(1) Connect an ammeter (0 to 10 ampere scale) in
series with the clutch coil terminal. Use a voltmeter
(0 to 20 volt scale) with clip-type leads for measuring
the voltage across the battery and the compressor
clutch coil.
(2) With the a/c heater mode control switch in any
a/c mode, the a/c heater control a/c switch in the ON
position, and the blower motor switch in the lowest
speed position, start the engine and run it at normal
idle.
(3) The compressor clutch coil voltage should read
within 0.2 volts of the battery voltage. If there is
voltage at the clutch coil, but the reading is not
within 0.2 volts of the battery voltage, test the clutch
coil feed circuit for excessive voltage drop and repair
as required. If there is no voltage reading at the
clutch coil, use a DRBIIItscan tool and the appro-
priate diagnostic information for testing of the com-
pressor clutch circuit. The following components
must be checked and repaired as required before you
can complete testing of the clutch coil:
²Fuses in the junction block and the Power Dis-
tribution Center (PDC)
²A/C heater mode control switch
²A/C compressor clutch relay
²A/C high pressure transducer
²A/C evaporator probe
²Powertrain Control Module (PCM)
²Body Control Module (BCM)
(4) The compressor clutch coil is acceptable if the
current draw measured at the clutch coil is 2.0 to 3.9
amperes with the electrical system voltage at 11.5 to
12.5 volts. This should only be checked with the work
area temperature at 21É C (70É F). If system voltage
is more than 12.5 volts, add electrical loads by turn-
ing on electrical accessories until the system voltage
drops below 12.5 volts.
(a) If the clutch coil current reading is four
amperes or more, the coil is shorted and should be
replaced.
(b) If the clutch coil current reading is zero, the
coil is open and should be replaced.
Fig. 4 COMPRESSOR CLUTCH - TYPICAL
1 - CLUTCH PLATE
2 - SHAFT KEY
3 - PULLEY
4 - COIL
5 - CLUTCH SHIMS
6 - SNAP RING
7 - SNAP RING
WJCONTROLS 24 - 13

VISCOUS HEATER
DESCRIPTION
DESCRIPTION
The diesel engine has an engine mounted mechan-
ical device called a Viscous Heater that is used to
heat the coolant coming from the engine to the
heater core. The Viscous Heater is driven by the
engine fan belt and has a electro-mechanical clutch
which is controlled by the HVAC control unit.
DESCRIPTION - VISCOUS HEATER CLUTCH
The basic viscous heater clutch assembly consists
of a stationary electromagnetic coil, a hub bearing
and pulley assembly and a clutch plate. The electro-
magnetic coil unit and the hub bearing and pulley
assembly are each retained on the nose of the com-
pressor front housing with snap rings (Fig. 17). The
clutch plate is keyed to the viscous heater shaft and
secured with a nut. These components provide the
means to engage and disengage the viscous heater
from the engine accessory drive belt.
OPERATION
OPERATION - VISCOUS HEATER
The Viscous Heater is driven by the engine fan
belt. The Viscous Heater has an electro-mechanical
clutch that receives a signal from the HVAC control
head and the Viscous Heater controller that ener-
gizes and engages the clutch. Once engaged theclutch allows the Viscous Heater to increase the tem-
perature of the coolant flowing to the heater core,
which provides heat the passenger compartment
quicker than normal engines without the Viscous
Heater. The Viscous Heater generates heat by means
of friction which heats a special Silicon Oil within its
housing which is then transferred to the engine cool-
ant when the coolant passes over fins within the
pump. Please note that the coolant is isolated from
the silicon oil within the pump housing. When
demand for passenger compartment heat decreases
the Viscous Heater clutch will receive an input from
the Viscous heater controller to disengage.
OPERATION - VISCOUS HEATER CLUTCH
When the clutch coil is energized, it magnetically
draws the clutch into contact with the pulley and
drives the viscous heater shaft. When the coil is not
energized the pulley freewheels on the clutch hub
bearing, which is part of the pulley. The viscous
heater clutch and coil are the only serviced parts on
the viscous heater assembly. If the viscous heater is
inoperative or damaged the entire assembly must be
replaced. The viscous heater clutch engagement is
controlled by several components: the viscous heater
controller, the engine powertrain control module and
the HVAC control head.
REMOVAL
REMOVAL - VISCOUS HEATER
(1) Drain the engine coolant(Refer to 7 - COOL-
ING/ENGINE - STANDARD PROCEDURE).
(2) Remove the engine accessory drive belt(Refer to
7 - COOLING/ACCESSORY DRIVE/DRIVE BELTS -
REMOVAL).
(3) Remove the heater hose clamps at the Viscous
Heater.
(4) Remove the heater hoses from the Viscous
Heater.
(5) Unplug the Viscous Heater clutch electrical
connector.
(6) Remove the bolts holding the Viscous Heater to
the mounting bracket.
(7) Remove the Viscous Heater from the vehicle.
REMOVAL - VISCOUS HEATER CLUTCH
(1) The viscous heater clutch can be serviced in
the vehicle and the cooling system does not have to
be drained.
(2) Disconnect and isolate the battery negative
cable.
(3) Remove the serpentine drive belt(Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
REMOVAL).
Fig. 17 CLUTCH ASSEMBLY- typical
1 - CLUTCH PLATE
2 - SHAFT KEY
3 - PULLEY
4 - COIL
5 - CLUTCH SHIMS
6 - SNAP RING
7 - SNAP RING
24 - 76 PLUMBINGWJ