Dodge Durango (DN). Manual — part 85

the potential for hunting between gears occurs with a
heavily loaded vehicle or on steep grades. When
hunting occurs, it is very objectionable because shifts
are frequent and accompanied by large changes in
noise and acceleration.

WIDE OPEN THROTTLE OPERATION

In wide-open throttle (WOT) mode, adaptive mem-

ory in the PCM assures that up-shifts occur at the
preprogrammed optimum speed. WOT operation is
determined from the throttle position sensor, which
is also a part of the emission control system. The ini-
tial setting for the WOT upshift is below the opti-
mum engine speed. As WOT shifts are repeated, the
PCM learns the time required to complete the shifts
by comparing the engine speed when the shifts occur
to the optimum speed. After each shift, the PCM
adjusts the shift point until the optimum speed is
reached. The PCM also considers vehicle loading,
grade and engine performance changes due to high
altitude in determining when to make WOT shifts. It
does this by measuring vehicle and engine accelera-
tion and then factoring in the shift time.

TRANSFER CASE LOW RANGE OPERATION

On four-wheel drive vehicles operating in low

range, the engine can accelerate to its peak more
rapidly than in Normal range, resulting in delayed
shifts and undesirable engine “flare.” The low range
governor pressure curve is also higher than normal
to initiate upshifts sooner. The PCM compares elec-
tronic vehicle speed signal used by the speedometer
to the transmission output shaft speed signal to
determine when the transfer case is in low range.

OVERDRIVE OFF SWITCH

DESCRIPTION

The overdrive OFF (control) switch is located in

the shift lever arm.

OPERATION

The switch is a momentary contact device that sig-

nals the PCM to toggle current status of the over-
drive function. At key-on, overdrive operation is
allowed. Pressing the switch once causes the over-
drive OFF mode to be entered and the overdrive OFF
switch lamp to be illuminated. Pressing the switch a
second time causes normal overdrive operation to be
restored and the overdrive lamp to be turned off. The
overdrive OFF mode defaults to ON after the ignition
switch is cycled OFF and ON. The normal position
for the control switch is the ON position. The switch
must be in this position to energize the solenoid and
allow a 3-4 upshift. The control switch indicator light
illuminates only when the overdrive switch is turned

to the OFF position, or when illuminated by the
transmission control module.

DIAGNOSIS AND TESTING

AUTOMATIC TRANSMISSION DIAGNOSIS

Automatic transmission problems can be a result of

poor engine performance, incorrect fluid level, incor-
rect linkage or cable adjustment, band or hydraulic
control pressure adjustments, hydraulic system mal-
functions or electrical/mechanical component mal-
functions. Begin diagnosis by checking the easily
accessible items such as: fluid level and condition,
linkage adjustments and electrical connections. A
road test will determine if further diagnosis is neces-
sary.

EFFECTS OF INCORRECT FLUID LEVEL

A low fluid level allows the pump to take in air

along with the fluid. Air in the fluid will cause fluid
pressures to be low and develop slower than normal.
If the transmission is overfilled, the gears churn the
fluid into foam. This aerates the fluid and causing
the same conditions occurring with a low level. In
either case, air bubbles cause fluid overheating, oxi-
dation and varnish buildup which interferes with
valve, clutch and servo operation. Foaming also
causes fluid expansion which can result in fluid over-
flow from the transmission vent or fill tube. Fluid
overflow can easily be mistaken for a leak if inspec-
tion is not careful.

CAUSES OF BURNT FLUID

Burnt, discolored fluid is a result of overheating

which has two primary causes.

(1) A result of restricted fluid flow through the

main and/or auxiliary cooler. This condition is usu-
ally the result of a faulty or improperly installed
drainback valve, a damaged main cooler, or severe
restrictions in the coolers and lines caused by debris
or kinked lines.

(2) Heavy duty operation with a vehicle not prop-

erly equipped for this type of operation. Trailer tow-
ing or similar high load operation will overheat the
transmission

fluid

if

the

vehicle

is

improperly

equipped. Such vehicles should have an auxiliary
transmission fluid cooler, a heavy duty cooling sys-
tem, and the engine/axle ratio combination needed to
handle heavy loads.

FLUID CONTAMINATION

Transmission fluid contamination is generally a

result of:

• adding incorrect fluid

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DESCRIPTION AND OPERATION (Continued)

• failure to clean dipstick and fill tube when

checking level

• engine coolant entering the fluid

• internal failure that generates debris

• overheat that generates sludge (fluid break-

down)

• failure to reverse flush cooler and lines after

repair

• 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.

OVERDRIVE ELECTRICAL CONTROLS

The overdrive off switch, valve body solenoid, case

connectors and related wiring can all be tested with
a 12 volt test lamp or a volt/ohmmeter. Check conti-
nuity of each component when diagnosis indicates
this is necessary. Refer to Group 8W, Wiring Dia-
grams, for component locations and circuit informa-
tion.

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46RE AUTOMATIC TRANSMISSION

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DIAGNOSIS AND TESTING (Continued)

Switch and solenoid continuity should be checked

whenever the transmission fails to shift into fourth
gear range.

GEARSHIFT CABLE

(1) The shifter lever and gate positions should be

in alignment with all transmission PARK, NEU-
TRAL, and gear detent positions.

(2) Engine starts must be possible with shift lever

in PARK or NEUTRAL gate positions only. Engine
starts must not be possible in any other gear posi-
tion.

(3) With shift lever handle in:

(a) PARK position—Apply forward force on cen-

ter of lever and remove pressure. Engine starts
must be possible.

(b) PARK position—Apply rearward force on cen-

ter of lever 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 lever. Transmission shall not be able to shift
from neutral to reverse.

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.

Note 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.

Note 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, note that

the front and rear clutches are applied simulta-
neously only in D range third and fourth gear. If the
transmission slips in third gear, either the front
clutch or the rear clutch is slipping.

If the transmission slips in fourth gear but not in

third gear, the overdrive clutch is slipping. By select-
ing another gear which does not use these clutches,
the slipping unit can be determined. For example, if
the transmission also slips in Reverse, the front
clutch is slipping. If the transmission does not slip in
Reverse, the rear clutch is slipping.

If slippage occurs during the 3-4 shift or only in

fourth gear, the overdrive clutch is slipping. Simi-
larly, if the direct clutch were to fail, the transmis-
sion would lose both reverse gear and overrun
braking in 2 position (manual second gear).

If the transmission will not shift to fourth gear, the

control switch, overdrive solenoid or related wiring
may also be the problem cause.

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 pressure test gauges

are required. Test Gauge C-3292 has a 100 psi range
and is used at the accumulator, governor, and front
servo ports. Test Gauge C-3293-SP has a 300 psi
range and is used at the rear servo and overdrive
ports where pressures exceed 100 psi.

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DIAGNOSIS AND TESTING (Continued)

Pressure Test Port Locations

Test ports are located at both sides of the transmis-

sion case (Fig. 66).

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.

The rear servo and governor pressure ports are at

the right rear of the transmission case. The overdrive
clutch pressure port is at the left rear of the case.

Test One - Transmission In Manual Low

NOTE: This test checks pump output, pressure reg-
ulation, and condition of the rear clutch and servo
circuit. Both test gauges are required for this test.

(1) Connect tachometer to engine. Position tachom-

eter so it can be observed from driver seat if helper
will be operating engine. Raise vehicle on hoist that
will allow rear wheels to rotate freely.

(2) Connect 100 psi Gauge C-3292 to accumulator

port. Then connect 300 psi Gauge C-3293-SP to rear
servo port.

(3) Disconnect throttle and gearshift cables from

levers on transmission valve body manual shaft.

(4) Have helper start and run engine at 1000 rpm.
(5) Move transmission shift lever fully forward

into 1 range.

(6) Gradually move transmission throttle lever

from full forward to full rearward position and note
pressures on both gauges:

• 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
throttle lever is moved rearward.

• Rear servo pressure should be same as line pres-

sure within 3 psi (20.68 kPa).

Test Two—Transmission In 2 Range

NOTE: This test checks pump output, line pressure
and pressure regulation. Use 100 psi Test Gauge
C-3292 for this test.

(1) Leave vehicle in place on hoist and leave Test

Gauge C-3292 connected to accumulator port.

(2) Have helper start and run engine at 1000 rpm.
(3) Move transmission shift lever one detent rear-

ward from full forward position. This is 2 range.

(4) Move transmission throttle lever from full for-

ward to full rearward position and read pressure on
gauge.

(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 Third Gear

NOTE: This test checks pressure regulation and
condition of the clutch circuits. Both test gauges
are required for this test.

(1) Turn OD switch off.

Clutch And Band Application Chart

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DIAGNOSIS AND TESTING (Continued)