ries the governor and parking sprag. An integral heli-
cal gear on the transfer shaft drives the differential
ring gear.
OPERATION
Transmission output is directed to an integral dif-
ferential by a transfer gear system in the following
input-to-output ratios:
FIRST 2.69:1
SECOND 1.55:1
THIRD 1.00:1
REVERSE 2.10:1
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - PRELIMINARY
DIAGNOSIS
Automatic transaxle malfunctions are usually
caused by the following general conditions:
²Improper fluid level/condition²Poor engine performance
²Improper engine or transaxle adjustments
²Transaxle hydraulic malfunctions
²Transaxle mechanical malfunctions
Diagnosis of transaxle problems should always
begin with checking the easily accessible variables:
²Fluid level and condition
²Gearshift cable adjustment
²Throttle valve cable adjustment
After verifying or adjusting these variables, road
test the vehicle to determine if the problem has been
corrected or that further diagnosis is necessary. If the
problem still exists, refer to the following diagnosis
charts to aid in determining the source or cause of
failure.
Hydraulic pressure tests should be performed
when a transaxle internal failure is suspected. The
hydraulic flow charts, in the Schematics and Dia-
grams section of this group, outline fluid flow and
hydraulic circuitry. Circuit operation is provided for
all gear ranges. Normal working pressures are also
supplied for each of the gear ranges.
21 - 24 31TH AUTOMATIC TRANSAXLERS
31TH AUTOMATIC TRANSAXLE (Continued)
ProCarManuals.com
CONDITION POSSIBLE CAUSES CORRECTION
BUZZING NOISE 1. Fluid Level Low 1. Add fluid and check for leaks.
2. Shift Cable Misassembled. 2. Route cable away from engine and bell
housing.
3. Valve Body Misassembled. 3. Remove, disassemble, inspect valve
body. Reassemble correctly if necessary.
Replace assembly if valves or springs are
damaged. Check for loose bolts or screws.
4. Pump Passages Leaking 4. Check pump for porous casting, scores
on mating surfaces and excess rotor
clearance. Repair as required. Loose pump
bolts.
5. Cooling System Cooler Plugged. 5. Flow check cooler circuit. Repair as
needed.
6.Overrunning Clutch Damaged. 6. Replace clutch.
SLIPS IN REVERSE ONLY 1. Fluid Level Low. 1. Add fluid and check for leaks.
2. Gearshift Linkage Misadjusted. 2. Adjust linkage.
3. Rear Band Misadjusted. 3. Adjust band.
4. Rear Band Worn. 4. Replace as required.
5. Hydraulic Pressure Too Low. 5. Perform hydraulic pressure tests to
determine cause.
6. Rear Servo Leaking. 6. Air pressure check clutch-servo operation
and repair as required.
7. Band Linkage Binding. 7. Inspect and repair as required.
SLIPS IN FORWARD
DRIVE RANGES1. Fluid Level Low. 1. Add fluid and check for leaks.
2. Fluid Foaming. 2. Check for high oil level, bad pump
gasket or seals, dirt between pump halves
and loose pump bolts. Replace pump if
necessary.
3. Throttle Linkage Misadjusted. 3. Adjust linkage.
4. Gearshift Linkage Misadjusted. 4. Adjust linkage.
5. Rear Clutch Worn. 5. Inspect and replace as needed.
6. Low Hydraulic Pressure Due to
Worn Pump, Incorrect Control
Pressure Adjustments, Valve Body
Warpage or Malfunction, Sticking
Governor, Leaking Seal Rings,
Clutch Seals Leaking, Servo Leaks,
Clogged Filter or Cooler Lines6. Perform hydraulic and air pressure tests
to determine cause.
7. Rear Clutch Malfunction, Leaking
Seals or Worn Plates.7. Air pressure check clutch-servo operation
and repair as required.
8. Overrunning Clutch Worn, Not
Holding (Slips in 1 Only).8. Replace Clutch.
SLIPS IN LOW GEAR9D9
ONLY, BUT NOT IN 1
POSITIONOverrunning Clutch Faulty. Replace overrunning clutch.
RS31TH AUTOMATIC TRANSAXLE21-29
31TH AUTOMATIC TRANSAXLE (Continued)
ProCarManuals.com
CONDITION POSSIBLE CAUSES CORRECTION
GROWLING, GRATING OR
SCRAPING NOISES1. Drive Plate Broken. 1. Replace.
2. Torque Converter Bolts Hitting
Dust Shield.2. Dust shield bent. Replace or repair.
3. Planetary Gear Set Broken/
Seized.3. Check for debris in oil pan and repair as
required.
4. Overrunning Clutch Worn/Broken. 4. Inspect and check for debris in oil pan.
Repair as required.
5. Oil Pump Components Scored/
Binding.5. Remove, inspect and repair as required.
6. Output Shaft Bearing or Bushing
Damaged.6. Remove, inspect and repair as required.
7. Clutch Operation Faulty. 7. Perform air pressure check and repair as
required.
8. Front and Rear Bands
Misadjusted.8. Adjust bands.
DRAGS OR LOCKS UP 1. Fluid Level Low. 1. Check and adjust level.
2. Clutch Dragging/Failed 2. Air pressure check clutch operation and
repair as required.
3. Front or Rear Band Misadjusted. 3. Adjust bands.
4. Case Leaks Internally. 4. Check for leakage between passages in
case.
5. Servo Band or Linkage
Malfunction.5. Air pressure check servo operation and
repair as required.
6. Overrunning Clutch Worn. 6. Remove and inspect clutch. Repair as
required.
7. Planetary Gears Broken. 7. Remove, inspect and repair as required
(look for debris in oil pan).
WHINE/NOISE RELATED
TO ENGINE SPEED1. Fluid Level Low. 1. Add fluid and check for leaks.
2. Shift Cable Incorrect Routing. 2. Check shift cable for correct routing.
Should not touch engine or bell housing.
TORQUE CONVERTER
LOCKS UP IN SECOND
AND/OR THIRD GEARLockup Solenoid, Relay or Wiring
Shorted/Open.Test solenoid, relay and wiring for
continuity, shorts or grounds. Replace
solenoid and relay if faulty. Repair wiring
and connectors as necessary.
HARSH 1-2 OR 2-3
SHIFTSLockup Solenoid Malfunction. Remove valve body and replace solenoid
assembly.
NO START IN PARK OR
NEUTRAL1. Gearshift Linkage/Cable
Misadjusted.1. Adjust linkage/cable.
2. Neutral Switch Wire Open/Cut. 2. Check continuity with test lamp. Repair
as required.
3. Neutral Switch Faulty. 3. Refer to service section for test and
replacement procedure.
4. Neutral Switch Connect Faulty. 4. Connectors spread open. Repair.
5. Valve Body Manual Lever
Assembly Bent/Worn/Broken.5. Inspect lever assembly and replace if
damaged.
21 - 30 31TH AUTOMATIC TRANSAXLERS
31TH AUTOMATIC TRANSAXLE (Continued)
ProCarManuals.com
CONDITION POSSIBLE CAUSES CORRECTION
NO REVERSE (OR SLIPS
IN REVERSE)1. Direct Clutch Pack (front clutch)
Worn.1. Disassemble unit and rebuild clutch
pack.
2. Rear Band Misadjusted. 2. Adjust band.
3. Front Clutch Malfunctioned/Burnt. 3. Air pressure test clutch operation.
Remove and rebuild if necessary.
OIL LEAKS (ITEMS
LISTED REPRESENT
POSSIBLE LEAK POINTS
AND SHOULD ALL BE
CHECKED.1. Fluid Lines and Fittings Loose/
Leaks/Damaged.1. Tighten fittings. If leaks persist, replace
fittings and lines if necessary.
2. Filler Tube (where tube enters
case) Leaks/Damaged.2. Replace tube seal. Inspect tube for
cracks in tube.
3. Pressure Port Plug Loose
Loose/Damaged.3. Tighten to correct torque. Replace plug
or reseal if leak persists.
4. Pan Gasket Leaks. 4. Tighten pan screws to 150 inch pounds.
If leaks persist, replace gasket. Do no over
tighten screws.
5. Valve Body Manual Lever Shaft
Seal Leaks/Worn.5. Replace shaft seal.
6. Rear Bearing Access Plate Leaks. 6. Replace gasket. Tighten screws.
7. Gasket Damaged or Bolts are
Loose.7. Replace bolts or gasket or tighten both.
8. Adapter/Extension Gasket
Damaged Leaks/Damaged.8. Replace gasket.
9. Neutral Switch Leaks/Damaged. 9. Replace switch and gasket.
10. Converter Housing Area Leaks. 10. Check for leaks at seal caused by worn
seal or burr on converter hub (cutting seal),
worn bushing, missing oil return, oil in front
pump housing or hole plugged. Check for
leaks past O-ring seal on pump or past
pump-to-case bolts; pump housing porous,
oil coming out vent due to overfill or leak
past front band shaft access plug.
11. Pump Seal Leaks/Worn/
Damaged.11. Replace seal.
12. Torque Converter Weld
Leak/Cracked Hub.12. Replace converter.
13. Case Porosity Leaks. 13. Replace case.
DIAGNOSIS AND TESTING - ROAD TEST
Prior to performing a road test, check the fluid
level and throttle valve cable adjustments.
During the road test, the transaxle should be oper-
ated in each position to check for slipping and any
variation in shifting.
If vehicle operates at high speeds, but has poor
acceleration, the converter's overrunning clutch may
be slipping. If acceleration is normal, but high throt-
tle opening is needed for high speeds, the stator
clutch may have seized.Observe closely for slipping or engine speed flare-
up. Slipping or flare-up in any gear usually indicates
clutch, band, or overrunning clutch problems. If the
condition is far advanced, an overhaul will probably
be necessary to restore normal operation.
In most cases, the clutch or band that is slipping
can be determined by noting the transaxle operation
in all selector positions and then comparing which
internal units are applied in those positions. The Ele-
ments±in±Use Chart provides a basis for road test
analysis.
RS31TH AUTOMATIC TRANSAXLE21-31
31TH AUTOMATIC TRANSAXLE (Continued)
ProCarManuals.com
CLUTCHES BANDS
LEVER START PARK
FRONT REAR LOCKUPOVER-
RUNNING(KICKDOWN) LOW/REV
POSITION SAFETY SPRAG FRONT REAR
P - PARK X X
R-
REVERSEXX
N-
NEUTRALX
D - DRIVE
First X X
Second X X
Third X X X
2-
SECOND
First X X
Second X X
1 - Low X X
The rear clutch is applied in both the D first gear
and 1 first gear positions. Also, the overrunning
clutch is applied in D first gear and the low/reverse
band is applied in 1 first gear position. If the trans-
axle slips in D range first gear, but does not slip in 1
first gear, the overrunning clutch is slipping. Simi-
larly, if the transaxle slips in any two forward gears,
the rear clutch is slipping.
Using the same procedure, the rear clutch and
front clutch are applied in D third gear. If the trans-
axle slips in third gear, either the front clutch or the
rear clutch is slipping. By selecting another gear that
does not use one of those units, the unit that is slip-
ping can be determined. If the transaxle also slips in
reverse, the front clutch is slipping. If the transaxle
does not slip in reverse, the rear clutch is slipping.
The process of elimination can be used to detect
any unit that slips and to confirm proper operation of
good units. Road testing can usually diagnose slip-
ping units, although the actual cause of the problem
may not be detected. Practically any condition can be
caused by leaking hydraulic circuits or sticking
valves.
Therefore, unless the condition is obvious, the
transaxle should never be disassembled until hydrau-
lic pressure tests have been performed.
DIAGNOSIS AND TESTING - HYDRAULIC
PRESSURE TESTS
Pressure testing is a very important step in the
diagnostic procedure. These tests usually reveal the
cause of most transaxle problems.
Before performing pressure tests, check fluid level
and condition, as well as control cable adjustments.
Fluid must be at operating temperature (150-200
degrees F.).
Install an engine tachometer. Raise vehicle on a
hoist that allows front wheels to turn, and position
tachometer so it can be read.
Disconnect throttle cable and shift cable from
transaxle levers so they can be controlled from out-
side the vehicle.
Attach 100 psi gauges (C-3292) to ports required
for test being conducted. A 300 psi gauge (C-3293SP)
is required for reverse pressure test at rear servo.
Test port locations are shown in (Fig. 1).
TEST ONE (SELECTOR IN 1)
(1) Attach gauges to line and low-reverse ports.
(2) Operate engine at 1000 rpm for test.
(3) Move selector lever on transaxle all the way
rearward (1 position).
(4) Read pressures on both gauges as throttle lever
on transaxle is moved from full clockwise position to
full counterclockwise position.
21 - 32 31TH AUTOMATIC TRANSAXLERS
31TH AUTOMATIC TRANSAXLE (Continued)
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(5) Line pressure should read 52 to 58 psi with
throttle lever clockwise. Pressure should gradually
increase to 80 to 88 psi.as lever is moved counter-
clockwise.
(6) Low/reverse pressure should read the same as
line pressure, within 3 psi.
(7) This tests pump output, pressure regulation,
and condition of rear clutch and rear servo hydraulic
circuits.
TEST TWO (SELECTOR IN 2)
(1) Attach one gauge to line pressure port, and tee
another gauge into lower cooler line fitting. This will
allow lubrication pressure readings to be taken.
(2) Operate engine at 1000 rpm for test.
(3) Move selector lever on transaxle one detent for-
ward from full rearward position. This is selector 2
position.
Fig. 1 Test Port Locations
1 - ACCUMULATOR VENT 8 - TO COOLER
2 - MANUAL THROTTLE LEVER SHAFT 9 - KICKDOWN RELEASE (FRONT CLUTCH)
3 - MANUAL SHIFT LEVER SHAFT 10 - KICKDOWN APPLY
4 - LOW-REVERSE PRESSURE 11 - CONVERTER CLUTCH SOLENOID CONNECTOR
5 - GOVERNER PRESSURE (BELOW DIFFERENTIAL COVER ON
RIGHT SIDE)12 - FROM COOLER
6 - LINE PRESSURE 13 - KICKDOWN BAND ADJUSTING SCREW
7 - KICKDOWN APPLY AT ACCUMULATOR
Fig. 2 Governor Pressure Tap
1 - GOVERNOR PRESSURE PLUG
RS31TH AUTOMATIC TRANSAXLE21-33
31TH AUTOMATIC TRANSAXLE (Continued)
ProCarManuals.com
(4) Read pressures on both gauges as throttle lever
on transaxle is moved from full clockwise position to
full counterclockwise position.
(5) Line pressure should read 52 to 58 psi with
throttle lever clockwise. Pressure should gradually
increase to 80 to 88 psi. as lever is moved counter-
clockwise.
(6) Lubrication pressure should be 10 to 25 psi
with lever clockwise and 10 to 35 psi with lever at
full counterclockwise.
(7) This tests pump output, pressure regulation,
and condition of rear clutch and lubrication hydraulic
circuits.
TEST THREE (SELECTOR IN D)
(1) Attach gauges to line and kickdown release
ports.
(2) Operate engine at 1600 rpm for test.
(3) Move selector lever on transaxle two detents
forward from full rearward position. This is selector
D position.
(4) Read pressures on both gauges as throttle lever
on transaxle is moved from full clockwise to the full
counterclockwise position.
(5) Line pressure should read 52 to 58 psi with
throttle lever clockwise. Pressure should gradually
increase to 80 to 88 psi. as lever is moved counter-
clockwise.
(6) Kickdown release is pressurized only in direct
drive and should be same as line pressure within 3
psi, up to kickdown point.
(7) This tests pump output, pressure regulation,
and condition of rear clutch, front clutch, and
hydraulic circuits.
TEST FOUR (SELECTOR IN REVERSE)
(1) Attach 300 psi gauge (C-3292SP) to low-reverse
port.
(2) Operate engine at 1600 rpm for test.
(3) Move selector lever on transaxle four detents
forward from full rearward position. This is selector
R position.
(4) Low/reverse pressure should read 180 to 220
psi with throttle lever clockwise. Pressure should
gradually increase to 260 to 300 psi. as lever is
moved counterclockwise.(5) This tests pump output, pressure regulation,
and condition of front clutch and rear servo hydraulic
circuits.
(6) Move selector lever on transaxle to D position
to check that low/reverse pressure drops to zero.
(7) This tests for leakage into rear servo, due to
case porosity, which can cause reverse band burn out.
TEST RESULT INDICATIONS
(1) If proper line pressure, minimum to maximum,
is found in any one test, the pump and pressure reg-
ulator are working properly.
(2) Low pressure in D, 1, and 2 but correct pres-
sure in R, indicates rear clutch circuit leakage.
(3) Low pressure in D and R, but correct pressure
in 1 indicates front clutch circuit leakage.
(4) Low pressure in R and 1, but correct pressure
in 2 indicates rear servo circuit leakage.
(5) Low line pressure in all positions indicates a
defective pump, a clogged filter, or a stuck pressure
regulator valve.
GOVERNOR PRESSURE
Test only if transaxle shifts at wrong vehicle
speeds when throttle cable is correctly adjusted.
(1) Connect a 100 psi gauge to governor pressure
port. It is located at lower right side of case, below
differential cover (Fig. 2).
(2) Operate transaxle in third gear to read pres-
sures. The governor pressure should respond
smoothly to changes in mph and should return to 0
to 3 psi when vehicle is stopped. High pressure
(above 3 psi) at standstill will prevent the transaxle
from downshifting.
THROTTLE PRESSURE
No gauge port is provided for throttle pressure.
Incorrect throttle pressure should be suspected if
part throttle upshift speeds are either delayed or
occur too early in relation to vehicle speed. Engine
runaway on shifts can also be an indicator of low
throttle pressure setting, or misadjusted throttle
cable.
In no case should throttle pressure be adjusted
until the transaxle throttle cable adjustment has
been verified to be correct.
21 - 34 31TH AUTOMATIC TRANSAXLERS
31TH AUTOMATIC TRANSAXLE (Continued)
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DIAGNOSIS AND TESTING - TORQUE
CONVERTER HOUSING FLUID LEAKAGE
When diagnosing converter housing fluid leaks,
three actions must be taken before repair:
(1) Verify proper transmission fluid level.
(2) Verify that the leak originates from the con-
verter housing area and is transmission fluid.
(3) Determine the true source of the leak.
Fluid leakage at or around the torque converter
area may originate from an engine oil leak (Fig. 3).
The area should be examined closely. Factory fill
fluid is red and, therefore, can be distinguished from
engine oil.
Some suspected converter housing fluid leaks may
not be leaks at all. They may only be the result of
residual fluid in the converter housing, or excess
fluid spilled during factory fill, or fill after repair.
Converter housing leaks have several potential
sources. Through careful observation, a leak source
can be identified before removing the transmission
for repair.
Pump seal leaks tend to move along the drive hub
and onto the rear of the converter (Fig. 3). Pump
o-ring or pump body leaks follow the same path as a
seal leak. Pump attaching bolt leaks are generally
deposited on the inside of the converter housing and
not on the converter itself. Pump seal or gasket leaks
usually travel down the inside of the converter hous-
ing (Fig. 3).
TORQUE CONVERTER LEAKAGE
Possible sources of torque converter leakage are:
²Torque converter weld leaks at the outside diam-
eter weld (Fig. 4).
²Torque converter hub weld (Fig. 4).
DIAGNOSIS AND TESTING - CLUTCH AND
SERVO AIR PRESSURE TESTS
A no drive condition might exist even with correct
fluid pressure, because of inoperative clutches or
bands. The inoperative units, clutches, bands, and
servos can be located through a series of tests. This
is done by substituting air pressure for fluid pressure
(Fig. 5).
The front and rear clutches, kickdown servo, and
low-reverse servo may be tested by applying air pres-
sure to their respective passages. To make air pres-
sure tests, proceed as follows:
NOTE: Compressed air supply must be free of all
dirt or moisture. Use a pressure of 30 psi.
Remove oil pan and valve body. Refer to Valve
Body for removal procedure.
FRONT CLUTCH
Apply air pressure to front clutch apply passage
and listen for a dull thud which indicates that front
clutch is operating. Hold air pressure on for a few
seconds and inspect system for excessive oil leaks.
Fig. 3 Converter Housing Leak Paths
1 - PUMP SEAL
2 - PUMP VENT
3 - PUMP BOLT
4 - PUMP GASKET
5 - CONVERTER HOUSING
6 - CONVERTER
7 - REAR MAIN SEAL LEAK
Fig. 4 Converter Leak PointsÐTypical
1 - OUTSIDE DIAMETER WELD
2 - TORQUE CONVERTER HUB WELD
3 - STARTER RING GEAR
4 - LUG
RS31TH AUTOMATIC TRANSAXLE21-35
31TH AUTOMATIC TRANSAXLE (Continued)
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