1994 JEEP CHEROKEE transmission

the drain port opens, spring force moves the valve up
exposing the second brake feed port for the shift to
second gear.
2-3 Shift Valve
The 2-3 shift valve (Fig. 19) controls 2-3 upshifts
and downshifts. The valve is actuated by the No. 1
valve body solenoid and by line pressure from the
manual valve and primary regulator valve.
When the transmission control module activates so-
lenoid No. 1, line pressure at the top of the 2-3 valve
is released through the solenoid drain port. Spring
tension moves the valve up to hold the valve in sec-ond gear position. As the solenoid is deactivated, line
pressure then moves the valve down exposing the di-
rect clutch feed port for the shift to third gear.
3-4 Shift Valve
The 3-4 shift valve (Fig. 20) is operated by the No.
2 solenoid and by line pressure from the manual
valve, 2-3 valve and primary regulator valve.
Energizing the No. 2 solenoid causes line pressure
at the top of the 3-4 valve to be released through the
solenoid valve drain port. Spring tension moves the
valve up exposing the overdrive clutch accumulator
feed port to apply the clutch.
Fig. 19 2-3 Shift Valve
Fig. 20 3-4 Shift Valve
21 - 164 AW-4 AUTOMATIC TRANSMISSIONJ

De-energizing the solenoid causes the drain port to
close. Line pressure then moves the valve down ex-
posing the overdrive brake accumulator feed port for
the shift to fourth gear.
In the 1-2 or 3 gearshift lever positions, line pres-
sure from the 2-3 shift valve is applied to the lower
end of the 3-4 valve. This holds the valve upward,
closing off the overdrive brake feed port preventing a
shift into fourth gear.
Second Coast Modulator Valve
The second coast modulator valve (Fig. 21) momen-
tarily reduces line pressure from the 1-2 shift valve.
This cushions application of the second coast brake.
The valve is operative when the shift lever and man-
ual valve are in the 3 position.
Low Coast Modulator Valve
The low coast modulator valve (Fig. 22) momen-
tarily reduces line pressure from the 2-3 shift valve
to cushion application of the first/reverse brake. The
valve operates when the shift lever and manual valve
are in the 1-2 position.
Accumulator Control Valve
The accumulator control valve (Fig. 23) cushions
clutch and brake application by reducing back pres-
sure to the accumulators when throttle opening is
small. The valve is operated by oil pump (line) pres-
sure and by throttle pressure.
Accumulators
Four accumulators are used to cushion application
of the clutches and brakes (Fig. 24). The accumula-tors consist of spring loaded pistons which dampen
the initial surge of apply pressure to provide smooth
engagement during shifts.
Control pressure from the accumulator control
valve is continuously applied to the back pressure
side of the accumulator pistons. This pressure plus
spring tension holds the pistons down. As line pres-
sure from the shift valves enters the opposite end of
the piston bore, control pressure and spring tension
momentarily delay application of full line pressure to
cushion engagement. The accumulators are all lo-
cated in the transmission case (Fig. 24).
Fig. 21 Second Coast Modulator Valve
Fig. 22 Low Coast Modulator Valve
Fig. 23 Accumulator Control Valve
JAW-4 AUTOMATIC TRANSMISSION 21 - 165

Transmission Valve Body Solenoids
Three solenoids are used (Fig. 25). The No. 1 and 2
solenoids control shift valve operation by applying or
releasing line pressure. The signal to apply or release
pressure is provided by the transmission control
module.The No. 3 solenoid controls operation of the torque
converter clutch. The solenoid operates in response to
signals from the transmission control module.
When the No. 1 and 2 solenoids are activated, the
solenoid plunger is moved off its seat opening the
drain port to release line pressure. When either sole-
noid is deactivated, the plunger closes the drain port.
The No. 3 solenoid operates in reverse. When the
solenoid is deactivated, the solenoid plunger is moved
off its seat opening the drain port to release line
pressure. When the solenoid is activated, the plunger
closes the drain port.
Fig. 24 Accumulators
Fig. 25 Transmission Valve Body Solenoids
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AW-4 TRANSMISSION DIAGNOSIS
INDEX
page page
General Diagnosis Information.............. 167
Hydraulic Pressure Test................... 168
Manual Shifting Test..................... 168Preliminary Inspection and Adjustment........ 167
Time Lag Test .......................... 169
Torque Converter Stall Test................ 169
GENERAL DIAGNOSIS INFORMATION
Shift points are controlled by the transmission con-
trol module (TCM). Before attempting repair, deter-
mine if a malfunction is electrical or mechanical.
The TCM used with the AW-4 transmission has a
self-diagnostic program compatible with the DRB II
scan tool. The tester will identify faults in the elec-
trical control system.Diagnosis should begin with the Preliminary In-
spection And Adjustment procedure. It is will help
determine if a problem is mechanical or electrical.
The first procedure step is Initial Inspection and Ad-
justment.
PRELIMINARY INSPECTION AND ADJUSTMENT
(1) Check and adjust transmission shift cable if
necessary.
Fig. 26 Preliminary Diagnosis Check Procedure
JAW-4 TRANSMISSION DIAGNOSIS 21 - 167

(2) Verify transmission throttle cable operation.
Repair or replace cable if necessary.
(3) Check engine throttle operation. Operate accel-
erator pedal and observe injector throttle plate move-
ment. Adjust linkage if throttle plate does not reach
wide open position.
(4) Check transmission fluid level when fluid is at
normal operating temperature. Start engine. Shift
transmission through all gear ranges then back to
Neutral. Correct level is to Full or Add mark on dip-
stick with engine at curb idle speed.
(5) Check and adjust park/neutral position switch
if necessary.
(6) Check throttle position sensor adjustment and
operation. Adjust the sensor if necessary.
MANUAL SHIFTING TEST
(1) This test determines if problem is related to
mechanical or electrical component.
(2) Stop engine and disconnect transmission con-
trol module or module fuse.
(3) Road test vehicle. Shift transmission into each
gear range. Transmission should operate as follows:
²lock in Park
²back up in Reverse
²not move in Neutral
²provide first gear only with shift lever in 1-2 posi-
tion
²operate in third gear only with shift lever in 3 po-
sition
²operate in overdrive fourth gear in D position
(4) If transmission operates as described, proceed
to next step. However, if forward gear ranges were
difficult to distinguish (all feel the same), or vehicle
would not back up, refer to diagnosis charts. Do not
perform stall or time lag tests.
CAUTION: Do not overspeed the engine during the
next test step. Ease off the throttle and allow the
vehicle to slow before downshifting.
(5) Continue road test. Manually downshift trans-
mission from D to 3, and from 3 to 1-2 position. Then
manually upshift transmission through forward
ranges again.
(6) If transmission operation is OK, perform stall,
time lag and pressure tests. If transmission shifting
problem is encountered, refer to diagnosis charts.
(7) If a problem still exists, continue testing with
DRB II scan tool.
HYDRAULIC PRESSURE TEST
PRESSURE TEST PROCEDURE
(1) Connect pressure test gauge to test port on pas-
senger side of transmission. Use Adapter 7554 to con-
nect gauge. Be sure test gauge has minimum
capacity of 300 psi (2100 kPa).(2) Be sure transmission fluid is at normal operat-
ing temperature.
(3) Apply parking brakes and block wheels.
WARNING: DO NOT ALLOW ANYONE TO STAND AT
THE FRONT OR REAR OF THE VEHICLE WHILE
PERFORMING THE FOLLOWING STEPS IN THE
PRESSURE TEST.
(4) Check and adjust engine curb idle speed.
(5) Apply service brakes.
(6) Shift transmission into D range and note line
pressure with engine at curb idle speed. Pressure
should be 61-to-70 psi (421-to-481 kPa).
(7) Press accelerator pedal to wide open throttle
position and note line pressure. Pressure should be
173-to-209 psi (1196-to-1442 kPa).
CAUTION: Do not maintain wide open throttle for
more than three or four seconds at a time.
(8) Shift transmission into Reverse and note line
pressure with engine at curb idle speed. Pressure
should be 75-to-90 psi (519-to-618 kPa).
(9) Press accelerator to wide open throttle position
and note line pressure in Reverse. Pressure should
be 213-to-263 psi (1471-to-1814 kPa).
CAUTION: Do not maintain wide open throttle for
more than three or four seconds at a time.
(10) If line pressure is not within specifications,
adjust transmission throttle cable and repeat pres-
sure test.
Fig. 27 Pressure Test Gauge Connection
21 - 168 AW-4 TRANSMISSION DIAGNOSISJ

PRESSURE TEST ANALYSIS
If pressures in D and Reverse are higher than
specified, 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, check for following:
²throttle cable loose, worn, binding or out of adjust-
ment
²throttle valve, downshift plug, throttle cam stick-
ing, 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.
(1) Be sure transmission fluid is at normal operat-
ing 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. On models
with NP249 transfer case, leave transfer case in 4H
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) Press accelerator pedal to wide open throttle
position and note maximum engine rpm. Stall speed
should be 2100 to 2400 rpm in D range.
CAUTION: Do not maintain wide open throttle for
more than 3-4 seconds at a time.(9) Release throttle and shift transmission into
Neutral. Allow transmission fluid to cool for 15-20
seconds.
(10) Shift transmission into Reverse.
(11) Press accelerator down to wide open throttle
position and note maximum engine rpm. Stall speed
should be 2100-to-2400 rpm in Reverse.
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.
(3) Apply parking brakes and turn off air condi-
tioning unit.
(4) Shift transfer case into 2H range. On models
with NP249 transfer case, leave transfer case in 4H
range.
(5) Start engine and check curb idle speed. Adjust
speed if necessary. Curb idle must be correct to en-
sure accurate test results.
(6) Shift transmission into Neutral and set stop
watch.
(7) During following test steps, start stop watch as
soon as shift lever reaches D and Reverse ranges.
JAW-4 TRANSMISSION DIAGNOSIS 21 - 169

(8) Shift transmission into D range and record
time it takes for engagement. Repeat test two more
times.
(9) Reset stop watch and shift transmission back to
Neutral.
(10) Shift transmission into Reverse and record
time it takes for engagement. Repeat test two more
times.
(11) Engagement time in D range should be a max-
imum of 1.2 seconds. Engagement time for Reverse
should be a maximum of 1.5 seconds.
TIME LAG TEST ANALYSIS
If engagement time is longer than specified for D
range, check for the following:²shift cable misadjusted
²line pressure low
²forward clutch worn
²overdrive clutch worn or damaged
If engagement time is longer than specified for Re-
verse, check for the following:
²shift cable misadjusted
²line pressure low
²direct clutch worn
²first/reverse brake worn
²overdrive clutch worn or damaged
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SERVICE DIAGNOSIS
JAW-4 TRANSMISSION DIAGNOSIS 21 - 171