Rpm JEEP CHEROKEE 1995 Service Owner's Guide

PRESSURE TEST ANALYSIS
If pressures in D and Reverse are higher than
specified in test, check for the following:
²throttle cable loose, worn, binding or out of adjust-
ment
²throttle valve, downshift plug, throttle cam, or pri-
mary regulator valve are sticking, worn or damaged
If pressures in D and Reverse are lower than spec-
ified in test, check for following:
²throttle cable loose, worn, binding or out of adjust-
ment
²throttle valve, downshift plug, or throttle cam
sticking, worn or damaged
²primary regulator valve sticking, worn, or dam-
aged
²oil pump gears or housing worn, or damaged
²overdrive clutch worn, or damaged
If pressures are low in D range only, check for fol-
lowing:
²forward clutch worn or damaged
²fluid leakage in D range circuit (component seal
and O-rings)
If pressures are low in Reverse only, check for fol-
lowing:
²shift cable and manual valve out of adjustment
²fluid leakage in reverse circuit (component seal
and O-rings)
²direct clutch worn or damaged
²first/reverse brake worn or damaged
TORQUE CONVERTER STALL TEST
Stall testing checks the holding ability of the trans-
mission clutches and brakes and of the torque con-
verter stator overrunning clutch.Stall speeds are
checked in both Drive and Reverse ranges with
the AW-4 transmission.
(1) Before starting test, be sure fluid level is cor-
rect and fluid is at normal operating temperature.
(2) Connect tachometer to engine. Position tachom-
eter so it can be viewed from drivers seat.
(3) Apply parking brakes and block wheels.
(4) Apply and hold service brakes.
(5) Shift transfer case into 2H position.
(6) Start engine.
WARNING: DO NOT ALLOW ANYONE TO STAND AT
THE FRONT OR REAR OF THE VEHICLE DURING
THE TEST.
(7) Shift transmission into D range.
(8) Open throttle completely and record maximum
engine rpm registered on tachometer. It takes any-
where from 4 to 10 seconds to reach maximum rpm.
However, once maximum rpm has been achieved,do
not hold wide open throttle for more than 3-4
seconds.CAUTION: Stalling the converter causes a rapid in-
crease in fluid temperature. To avoid fluid overheat-
ing, hold wide open throttle for no more than 4
seconds after reaching peak rpm. In addition, if
more than one stall test is required, run the engine
at 1000 rpm with the transmission in Neutral for at
least 20 seconds to cool the fluid.
(9) Stall speed should be in 2100-2400 rpm range
in Drive.
(10) Release throttle, shift transmission into Neu-
tral, and run engine for 20-30 seconds to cool fluid.
(11) Shift transmission into Reverse.
(12) Repeat stall test described in step (8).
(13) Stall speed in Reverse should also be in 2100-
2400 rpm range.
(14) Release accelerator pedal, shift transmission
into Neutral, and run engine for 20-30 seconds to
cool fluid.
STALL SPEED TEST ANALYSIS
If engine rpm is lower than specified in D and Re-
verse, check for the following:
²engine output/performance insufficient
²stator overrunning clutch in torque converter not
holding if engine speed was 1500 rpm or less.
If stall speed in D range is higher than specified,
check for the following:
²line pressure low
²forward clutch slipping
²No. 2 one-way clutch not holding
²overdrive one-way clutch not holding
If stall speed in Reverse was higher than specified,
check for the following:
²line pressure low
²direct clutch slipping
²first/ reverse brake slipping
²overdrive one-way clutch not holding
If stall speeds were higher than specified in both D
and Reverse, check for the following:
²low fluid level
²line pressure low
²overdrive one-way clutch not holding
TIME LAG TEST
This test checks general condition of the overdrive
clutch, forward clutch, rear clutch and first/reverse
brake. Condition is indicated by the amount of time
required for clutch/brake engagement with the en-
gine at curb idle speed. Engagement time is mea-
sured for D and Reverse positions. A stop watch is
recommended for test accuracy.
TEST PROCEDURE
(1) Check and adjust transmission fluid level if
necessary.
(2) Bring transmission to normal operating tem-
perature.
21 - 178 AW-4 TRANSMISSION DIAGNOSISJ

VEHICLE VIBRATION
Vehicle vibration can be caused by:
²Tire/wheel unbalance or excessive runout
²Defective tires with extreme tread wear
²Nylon overlay flat spots (performance tires only)
²Incorrect wheel bearing adjustment (if applicable)
²Loose or worn suspension/steering components
²Certain tire tread patterns
²Incorrect drive shaft angles or excessive drive
shaft/yoke runout
²Defective or worn U-joints
²Excessive brake rotor or drum runout
²Loose engine or transmission supports/mounts
²And by engine operated accessories
Refer to the appropriate Groups in this man-
ual for additional information.
VIBRATION TYPES
There are two types of vehicle vibration:
²Mechanical
²Audible.
Mechanical vehicle vibration can be felt through
the seats, floor pan and/or steering wheel.
Audible vehicle vibration is heard above normal
background noise. The sound can be a droning or
drumming noise.
Vibrations are sensitive to change in engine torque,
vehicle speed or engine speed.
ENGINE TORQUE SENSITIVE VIBRATION
This vibration can be increased or decreased by:
²Accelerating
²Decelerating
²Coasting
²Maintaining a constant vehicle speed
VEHICLE SPEED SENSITIVE VIBRATION
This vibration condition always occurs at the same
vehicle speed regardless of the engine torque or en-
gine speed.
ENGINE SPEED (RPM) SENSITIVE VIBRATION
This vibration occurs at varying engine speeds. It
can be isolated by increasing or decreasing the en-
gine speed with the transmission in NEUTRAL posi-
tion.
VIBRATION DIAGNOSIS
A vibration diagnosis should always begin with a
10 mile (16 km) trip (to warm the vehicle and tires).
Then a road test to identify the vibration. Corrective
action should not be attempted until the vibration
type has been identified via a road test.
During the road test, drive the vehicle on a smooth
surface. If vibration exists, note and record the fol-
lowing information:²Identify the vehicle speed range when the vibra-
tion occurs
²Identify the type of vibration
²Identify the vibration sensitivity
²Determine if the vibration is affected by changes
in vehicle speed, engine speed and engine torque.
When the vibration has been identified, refer to the
Vibration Diagnosis chart for causes. Consider cor-
recting only those causes coded in the chart that are
related to the vibration condition.
Refer to the following cause codes and descriptions
for explanations when referring to the chart.
TRRÐTire and Wheel Radial Runout:Vehicle
speed sensitive, mechanical vibration. The runout
will not cause vibration below 20 mph (32 km/h).
WHÐWheel Hop:Vehicle speed sensitive, me-
chanical vibration. The wheel hop generates rapid
up-down movement in the steering wheel. The vibra-
tion is most noticeable in the 20 - 40 mph (32 - 64
km/h) range. The wheel hop will not cause vibration
below 20 mph (32 km/h). Wheel hop is caused by a
tire/wheel that has a radial runout of more than
0.045 of-an-inch (1.14 mm). If wheel runout is accept-
able and combined runout cannot be reduced by re-
positioning the tire on wheel, replace tire.
TBÐTire/Wheel Balance:Vehicle speed sensitive,
mechanical vibration. Static tire/wheel unbalance
will not cause vibration below 30 mph (46 km/h). Dy-
namic tire/wheel unbalance will not cause vibration
below 40 mph (64 km/h).
TLRÐTire/Wheel Lateral runout:Vehicle speed
sensitive, mechanical vibration. The runout will not
cause vibration below 50 - 55 mph (80 - 88 km/h). Ex-
cessive lateral runout will also cause front-end
shimmy.
TWÐTire Wear:Vehicle speed sensitive, audible
vibration. Abnormal tire wear causes small vibration
in the 30 - 55 mph (88 km/h) range. This will pro-
duce a whine noise at high speed. The whine will
change to a growl noise when the speed is reduced.
WÐTire Waddle:Vehicle speed sensitive, mechan-
ical vibration. Irregular tire uniformity can cause
side-to-side motion during speeds up to 15 mph (24
km/h). If the motion is excessive, identify the defec-
tive tire and replace it.
UAJÐUniversal Joint (Drive Shaft) Angles:
Torque/vehicle speed sensitive, mechanical/audible vi-
bration. Incorrect drive shaft angles cause mechani-
cal vibration below 20 mph (32 km/h) and in the 70
mph (112 km/h) range. The incorrect angles can also
produce an audible vibration in the 20 - 50 mph (32 -
80 km/h) range. Caster adjustment could be required
to correct the angles.
UJÐUniversal Joints:Engine torque/vehicle
speed sensitive, mechanical/audible vibration. If the
22 - 10 WHEELS AND TIRESJ

U-joint is worn it will cause vibration with almost
any vehicle speed/engine torque condition.
DSYÐDrive Shaft and Yokes:Vehicle speed sen-
sitive, mechanical/audible vibration. The condition
will not cause vibration below 35 mph (56 km/h). Ex-
cessive runout, unbalance or dents and bends in the
shaft will cause the vibration. Identify the actual
cause and repair/replace as necessary.
WBÐWheel Bearings:Vehicle speed sensitive,
mechanical/audible vibration. Loose wheel bearings
cause shimmy-like vibration at 35 mph (56 km/h)
and above. Worn bearings will also produce a growl
noise at low vehicle speed and a whine noise at high
vehicle speed. The wheel bearings must be adjusted
or replaced, as applicable.
ANÐAxle Noise:Engine torque/vehicle speed sen-
sitive, mechanical/audible vibration. The axle will not
cause mechanical vibration unless the axle shaft is
bent. Worn or damaged axle pinion shaft or differen-
tial gears and bearings will cause noise. Replace the
defective component(s) as necessary.
SSCÐSuspension and Steering Components:
Vehicle speed sensitive, mechanical vibration. Worn
suspension/steering components can cause mechani-
cal vibration at speeds above 20 mph (32 km/h).
Identify and repair or replace the defective compo-
nent(s).EAÐEngine Driven Accessories:Engine speed
sensitive, mechanical/audible vibration. Vibration can
be caused by loose or broken A/C compressor, PS
pump, water pump, generator or brackets, etc. Usu-
ally more noticeable when the transmission is shifted
into the NEUTRAL position and the engine speed
(rpm) increased. Inspect the engine driven accesso-
ries in the engine compartment. Repair/replace as
necessary.
ADBÐAccessory Drive Belts:Engine speed sen-
sitive, audible vibration. Worn drive belts can cause a
vibration that produces either a droning, fluttering or
rumbling noise. Inspect the drive belt(s) and tighten/
replace as necessary.
DEMÐDamaged Engine or Transmission Sup-
port Mounts:Engine speed sensitive, mechanical/
audible vibration. If a support mount is worn, noise
or vibration will occur. Inspect the support mounts
and repair/replace as necessary.
ESÐExhaust System:Engine speed sensitive,
mechanical/audible vibration. If loose exhaust compo-
nents contact the vehicle body they will cause noise
and vibration. Inspect the exhaust system for loose,
broken and mis-aligned components and repair/re-
place as necessary.
VIBRATION DIAGNOSIS
JWHEELS AND TIRES 22 - 11

REFRIGERANT OIL
It is important to have the correct amount of oil in
the A/C system. This will ensure proper lubrication of
the compressor. Too little oil will result in damage to
the compressor. Too much oil will reduce the cooling
capacity of the system.
The oil used in the SD7H15 compressor is a poly-
alkylene glycol synthetic oil SP-20 PAG, wax-free re-
frigerant oil. Only refrigerant oil of the same type
should be used to service the system. Do not use any
other oil. The oil container should be kept tightly
capped until it is ready for use and then capped after
use to prevent contamination. Refrigerant oil will
quickly absorb any moisture it comes in contact with.
OIL LEVEL CHECK
It will not be necessary to check oil level in the
compressor or to add oil unless there has been an oil
loss. This may be due to a rupture or leak from a
line, shaft seal, evaporator or condenser. Oil loss at a
leak point will be evident by the presence of a wet,
shiny surface around the leak.
When an A/C system is assembled at the factory,
all components (except the compressor) are refriger-
ant oil free. After the system has been charged and
operated, the oil in the compressor is dispersed
through the system. The receiver-drier, evaporator,
condenser and compressor will retain a significant
amount of oil.
Refrigerant oil must be added when a receiver-
drier, evaporator, condenser or compressor are re-
placed. When the compressor is replaced, the oil
must be drained from the replaced compressor and
measured. Drain all the oil from the new compressor.
Add back into the new compressor the amount of oil
that was drained out of the old compressor.
Add an additional 30 ml (1 fluid oz.) of com-
pressor oil to the system when a receiver-drier,
condenser or evaporator is replaced.
AIR CONDITIONING PERFORMANCE TESTS
Humidity has an important bearing on the temper-
ature of the air delivered to the vehicle's interior. It
is important to understand the effect humidity has
on the performance of the system. When humidity is
high, the evaporator has to perform a double duty. It
must lower the air temperature and the temperature
of the moisture carried in the air. Condensing the
moisture in the air transfers a great deal of heat en-
ergy into the evaporator fins and tubing. This re-
duces the amount of heat the evaporator can absorb
from the air. High humidity greatly reduces the evap-
orator's ability to lower the temperature of the air.Evaporator capacity used to reduce the amount of
moisture in the air is not wasted. Wringing some of
the moisture out of the air entering the vehicle adds
to the comfort of the passengers. However, an owner
may expect too much from their air conditioning sys-
tem on humid days. A performance test is the best
way to determine whether or not the system is per-
forming up to standard. This test also provides valu-
able clues to the possible cause of trouble.
Air temperature in test room must be 21ÉC (70ÉF)
minimum for this test.
(1) Connect a Tachometer and manifold gauge set.
(2) Set A/C controls to Max A/C, temperature lever
on full cool and blower on high.
(3) Start engine and adjust idle to 1,000 RPM with
A/C clutch engaged.
(4) Engine should be warmed up with doors, win-
dows and hood closed.
(5) Insert a thermometer in the left center A/C out-
let. Operate the A/C and engine for 5 minutes. The
A/C clutch may cycle depending on ambient temper-
atures.
(6) After 5 minutes note the discharge air temper-
ature. If the clutch cycles, take the reading before
the clutch disengages.
(7) On LHD XJ vehicles open the hood and discon-
nect vacuum line going to the heater water control
valve. Observe the valve arm for movement as the
line is disconnected. Plug the vacuum line to prevent
leakage. If it does not move repair vacuum circuit.
(8) Operate the A/C for 2 more minutes and take
the discharge air temperature reading again. On XJ
vehicles if the temperature increased by more than
2ÉC (5ÉF) check the blend air door cable for correct
operation.
(9) Compare the discharge air temperature to the
A/C Performance (Temperature and Pressure) Chart.
If the discharge air temperature is high, refer to Re-
frigerant Leak Testing and Refrigerant System Diag-
nosis Chart.
(10) Compare the compressor discharge and suc-
tion pressures to the A/C Performance (Temperature
and Pressure) Chart. If the compressor discharge or
suction pressure is not normal, check the operation of
the refrigerant system. Refer to Refrigerant System
Diagnosis Chart.
If pressures are abnormal, refer to the Pressure
and Performance Diagnosis Charts.
The following chart have been developed for quick
reference.
24 - 12 HEATING AND AIR CONDITIONINGJ