Jeep XJ. Manual — part 398
• failure to replace contaminated converter after
repair
The use of non recommended fluids can result in
transmission failure. The usual results are erratic
shifts, slippage, abnormal wear and eventual failure
due to fluid breakdown and sludge formation. Avoid
this condition by using recommended fluids only.
The dipstick cap and fill tube should be wiped
clean before checking fluid level. Dirt, grease and
other foreign material on the cap and tube could fall
into the tube if not removed beforehand. Take the
time to wipe the cap and tube clean before withdraw-
ing the dipstick.
Engine coolant in the transmission fluid is gener-
ally caused by a cooler malfunction. The only remedy
is to replace the radiator as the cooler in the radiator
is not a serviceable part. If coolant has circulated
through the transmission for some time, an overhaul
may also be necessary; especially if shift problems
had developed.
The transmission cooler and lines should be
reverse flushed whenever a malfunction generates
sludge and/or debris. The torque converter should
also be replaced at the same time.
Failure to flush the cooler and lines will result in
recontamination. Flushing applies to auxiliary cool-
ers as well. The torque converter should also be
replaced whenever a failure generates sludge and
debris. This is necessary because normal converter
flushing procedures will not remove all contami-
nants.
PRELIMINARY DIAGNOSIS
Two basic procedures are required. One procedure
for vehicles that are drivable and an alternate proce-
dure for disabled vehicles (will not back up or move
forward).
VEHICLE IS DRIVEABLE
(1) Check for transmission fault codes using DRB
scan tool.
(2) Check fluid level and condition.
(3) Adjust throttle and gearshift linkage if com-
plaint was based on delayed, erratic, or harsh shifts.
(4) Road test and note how transmission upshifts,
downshifts, and engages.
(5) Perform stall test if complaint is based on slug-
gish acceleration. Or, if abnormal throttle opening is
needed to maintain normal speeds with a properly
tuned engine.
(6) Perform hydraulic pressure test if shift prob-
lems were noted during road test.
(7) Perform air-pressure test to check clutch-band
operation.
VEHICLE IS DISABLED
(1) Check fluid level and condition.
(2) Check for broken or disconnected gearshift or
throttle linkage.
(3) Check for cracked, leaking cooler lines, or loose
or missing pressure-port plugs.
(4) Raise and support vehicle on safety stands,
start engine, shift transmission into gear, and note
following:
(a) If propeller shaft turns but wheels do not,
problem is with differential or axle shafts.
(b) If propeller shaft does not turn and transmis-
sion is noisy, stop engine. Remove oil pan, and
check for debris. If pan is clear, remove transmis-
sion and check for damaged drive plate, converter,
oil pump, or input shaft.
(c) If propeller shaft does not turn and transmis-
sion is not noisy, perform hydraulic-pressure test to
determine if problem is hydraulic or mechanical.
PARK/NEUTRAL POSITION SWITCH
The center terminal of the park/neutral position
switch is the starter-circuit terminal. It provides the
ground for the starter solenoid circuit through the
selector lever in PARK and NEUTRAL positions only.
The outer terminals on the switch are for the backup
lamp circuit.
SWITCH TEST
To test the switch, remove the wiring connector.
Test for continuity between the center terminal and
the transmission case. Continuity should exist only
when the transmission is in PARK or NEUTRAL.
Shift the transmission into REVERSE and test
continuity at the switch outer terminals. Continuity
should exist only when the transmission is in
REVERSE. Continuity should not exist between the
outer terminals and the case.
Check gearshift linkage adjustment before replac-
ing a switch that tests faulty.
GEARSHIFT CABLE
(1) The floor shifter lever and gate positions
should be in alignment with all transmission PARK,
NEUTRAL, and gear detent positions.
(2) Engine starts must be possible with floor shift
lever in PARK or NEUTRAL gate positions only.
Engine starts must not be possible in any other gear
position.
(3) With floor shift lever handle push-button not
depressed and lever in:
(a) PARK position—Apply forward force on cen-
ter of handle and remove pressure. Engine starts
must be possible.
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AUTOMATIC TRANSMISSION—30RH
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DIAGNOSIS AND TESTING (Continued)
(b) PARK position—Apply rearward force on cen-
ter of handle and remove pressure. Engine starts
must be possible.
(c) NEUTRAL position—Normal position. Engine
starts must be possible.
(d) NEUTRAL position—Engine
running
and
brakes applied, apply forward force on center of
shift handle. Transmission shall not be able to shift
from neutral to reverse.
THROTTLE VALVE CABLE
Transmission throttle valve cable adjustment is
extremely important to proper operation. This adjust-
ment positions the throttle valve, which controls shift
speed, quality, and part-throttle downshift sensitivity.
If cable setting is too loose, early shifts and slip-
page between shifts may occur. If the setting is too
tight, shifts may be delayed and part throttle down-
shifts may be very sensitive. Refer to the Adjust-
ments section for the proper adjustment procedure.
ROAD TESTING
Before road testing, be sure the fluid level and con-
trol
cable
adjustments
have
been
checked
and
adjusted if necessary. Verify that diagnostic trouble
codes have been resolved.
Observe engine performance during the road test.
A poorly tuned engine will not allow accurate analy-
sis of transmission operation.
Operate the transmission in all gear ranges. Check
for shift variations and engine flare which indicates
slippage. Note if shifts are harsh, spongy, delayed,
early, or if part throttle downshifts are sensitive.
Slippage indicated by engine flare, usually means
clutch, band or overrunning clutch problems. If the
condition is advanced, an overhaul will be necessary
to restore normal operation.
A slipping clutch or band can often be determined
by comparing which internal units are applied in the
various gear ranges. The Clutch and Band Applica-
tion chart provides a basis for analyzing road test
results.
ANALYZING ROAD TEST
Refer to the Clutch and Band Application chart
and note which elements are in use in the various
gear ranges.
Verify that the rear clutch is applied in all forward
ranges (D, 2, 1). The transmission overrunning clutch
is applied in first gear (D, 2 and 1 ranges) only. The
rear band is applied in 1 and R range only.
Verify that the overdrive clutch is applied only in
fourth gear and the overdrive direct clutch and over-
running clutch are applied in all ranges except fourth
gear. For example: If slippage occurs in first gear in
D and 2 range but not in 1 range, the transmission
overrunning clutch is faulty. Similarly, if slippage
occurs in any two forward gears, the rear clutch is
slipping.
Applying the same method of analysis, verify that
the front and rear clutches are applied simulta-
neously only in D range third gear. If the transmis-
sion slips in third gear, either the front clutch or the
rear clutch is slipping.
If slippage occurs during the third gear and the
direct clutch were to fail, the transmission would lose
both reverse gear and overrun braking in 2 position
(manual second gear). If the transmission slips in
any other forward gears, the transmission rear clutch
is probably slipping.
This process of elimination can be used to identify
a slipping unit and check operation. Proper use of
the Clutch and Band Application Chart is the key.
Although road test analysis will help determine the
slipping unit, the actual cause of a malfunction usu-
ally cannot be determined until hydraulic and air
pressure tests are performed. Practically any condi-
tion can be caused by leaking hydraulic circuits or
sticking valves.
Unless a malfunction is obvious, such as no drive
in D range first gear, do not disassemble the trans-
mission. Perform the hydraulic and air pressure tests
to help determine the probable cause.
HYDRAULIC PRESSURE TEST
Hydraulic test pressures range from a low of one
psi (6.895 kPa) governor pressure, to 300 psi (2068
kPa) at the rear servo pressure port in reverse.
An accurate tachometer and two test gauges are
required for the pressure test. Test Gauge C-3292
has a 100 psi range and is used at the accumulator,
Fig. 56 Clutch And Band Application
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AUTOMATIC TRANSMISSION—30RH
21 - 129
DIAGNOSIS AND TESTING (Continued)
governor, and front servo pressure ports. Test Gauge
C-3293-SP has a 300 psi range and is used at the
rear servo port and overdrive test ports where pres-
sures are higher. In cases where two test gauges are
required, the 300 psi gauge can be used at any of the
other test ports.
Pressure Test Port Locations
Pressure test ports locations are provided at the
accumulator, front servo, and rear servo, governor
passage, and overdrive clutch pressure passage (Fig.
57), (Fig. 58) and (Fig. 59).
Line pressure is checked at the accumulator port
on the right side of the case. The front servo pressure
port is at the right side of the case just behind the
filler tube opening.
Connect a tachometer to the engine. Position the
tachometer so it can be observed from under the
vehicle. Raise the vehicle on a hoist that will allow
the wheels to rotate freely.
PRESSURE TEST PROCEDURE
Test One - Transmission In 1 Range
This test checks pump output, pressure regulation,
and condition of the rear clutch and servo circuit.
Test Gauges C-3292 and C-3293-SP are required for
this test. Gauge C-3292 has a 100 psi range. Gauge
C-3293-SP has a 300 psi range.
(1) Connect 100 psi Gauge C-3292 to accumulator
port.
(2) Connect 300 psi Gauge C-3293-SP to rear servo
port (Fig. 57) and (Fig. 58).
(3) Disconnect throttle and gearshift rods from
manual and throttle levers.
(4) Start and run engine at 1000 rpm.
(5) Move shift lever (on manual lever shaft) all the
way forward into 1 range.
(6) Move transmission throttle lever from full for-
ward to full rearward position and note pressures on
both gauges.
(7) Line pressure at accumulator port should be
54-60 psi (372-414 kPa) with throttle lever forward
and gradually increase to 90-96 psi (621-662 kPa) as
lever is moved rearward.
(8) Rear servo pressure should be same as line
pressure within 3 psi (20.68 kPa).
Test Two - Transmission In 2 Range
This test checks pump output and pressure regula-
tion. Use 100 psi Test Gauge C-3292 for this test.
(1) Connect test gauge to accumulator pressure
port (Fig. 57) and (Fig. 58).
(2) Start and run engine at 1000 rpm.
(3) Move shift lever on valve body manual lever
shaft, one detent rearward from full forward position.
This is 2 range.
(4) Move transmission throttle lever from full for-
ward to full rearward position and read pressure at
both gauges.
Fig. 57 Pressure Test Ports At Side Of Case
1 – REAR SERVO PORT
2 – LINE PRESSURE PORT
3 – FRONT SERVO PORT
Fig. 58 Pressure Test Ports At Rear Of Case—2WD
1 – GOVERNOR PRESSURE PORT
2 – REAR SERVO PRESSURE PORT
Fig. 59 Pressure Test Ports At Rear Of Case—4WD
1 – ADAPTER HOUSING
2 – GOVERNOR PRESSURE PORT PLUG
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AUTOMATIC TRANSMISSION—30RH
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DIAGNOSIS AND TESTING (Continued)
(5) Line pressure should be 54-60 psi (372-414
kPa) with throttle lever forward and gradually
increase to 90-96 psi (621-662 kPa) as lever is moved
rearward.
Test Three - Transmission In D Range
This test checks pressure regulation and condition
of the clutch circuits. Use both pressure Test Gauges
C-3292 and C-3293-SP for this test.
(1) Connect test gauges to accumulator and front
servo ports (Fig. 57) and (Fig. 58). Use either test
gauge at the two ports.
(2) Start and run engine at 1600 rpm for this test.
(3) Move selector lever to D range. This is two
detents rearward from full forward position.
(4) Read pressures on both gauges as transmission
throttle lever is moved from full forward to full rear-
ward position.
(5) Line pressure should be 54-60 psi (372-414
kPa) with throttle lever forward and gradually
increase as lever is moved rearward.
(6) Front servo is pressurized only in D range and
should be same as line pressure within 3 psi (21 kPa)
up to downshift point.
Test Four - Transmission In Reverse
This test checks pump output, pressure regulation
and the front clutch and rear servo circuits. Use 300
psi Test Gauge C-3293-SP for this test.
(1) Connect 300 psi gauge to rear servo port (Fig.
57) and (Fig. 58).
(2) Start and run engine at 1600 rpm for test.
(3) Move valve body selector lever four detents
rearward from the full forward position. This is
Reverse range.
(4) Move throttle lever all way forward then all
way rearward and note gauge readings.
(5) Pressure should be 145 - 175 psi (1000-1207
kPa) with lever forward and increase to 230 - 280 psi
(1586-1931 kPa) as lever is moved rearward.
Test Five - Governor Pressure
This test checks governor operation by measuring
governor pressure response to changes in engine
speed. It is usually not necessary to check governor
operation unless shift speeds are incorrect or if the
transmission will not downshift.
(1) Connect 100 psi Test Gauge C-3292 to governor
pressure port (Fig. 57) and (Fig. 58).
(2) Move shift lever to D range.
(3) Start and run engine at curb idle speed and
note pressure. At idle and with vehicle stopped, pres-
sure should be zero to 1.5 psi maximum. If pressure
exceeds this figure, governor valve or weights are
sticking open.
(4) Slowly increase engine speed and observe
speedometer and pressure test gauge. Governor pres-
sure should increase in proportion to vehicle speed.
(5) Pressure rise should be smooth and drop back
to 0 to 1.5 psi when wheels stop rotating.
(6) Compare results of pressure tests with analysis
charts (Fig. 60).
AIR TESTING TRANSMISSION CLUTCH AND
BAND OPERATION
Air-pressure testing can be used to check transmis-
sion front/rear clutch and band operation. The test
can be conducted with the transmission either in the
vehicle or on the work bench, as a final check, after
overhaul.
Air-pressure testing requires that the oil pan and
valve body be removed from the transmission. The
servo and clutch apply passages are shown (Fig. 61).
TEST CONDITION
INDICATION
Line pressure OK during
any one test
Pump and regulator valve
OK
Line pressure OK in R
but low in D, 2, 1
Leakage in rear clutch
area (servo, clutch seals,
governor support seal
rings on park gear)
Pressure OK in 1, 2 but
low in D3 and R
Leakage in front clutch
area (servo, clutch seals,
retainer bore, pump seal
rings)
Pressure OK in 2 but low
in R and 1
Leakage in rear servo
Front servo pressure in 2
Leakage in servo (broken
servo ring or cracked
servo piston)
Pressure low in all
positions
Clogged filter, stuck
pressure regulator valve,
worn or defective pump
Governor pressure too
high at idle speed
Governor valve sticking
open
Governor pressure low at
all mph figures
Governor valve sticking
closed
Lubrication pressure low
at all throttle positions
Clogged drainback valve,
oil cooler or lines, seal
rings leaking, output shaft
plugged with devris, worn
bushings in pump or
clutch retainer
Fig. 60 Pressure Test Analysis
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AUTOMATIC TRANSMISSION—30RH
21 - 131
DIAGNOSIS AND TESTING (Continued)
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