Jeep 1996 Grand Cherokee Service Manual - page 1148
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 on
4-speed models. A road test will determine if further
diagnosis is necessary.
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 control module 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.
Then test for continuity between the center terminal
and the transmission case. Continuity should exist
only when the transmission is in PARK or NEU-
TRAL.
Shift the transmission into REVERSE and test
continuity at the switch outer terminals (Fig. 9).
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 bad.
CHECKING FLUID LEVEL AND CONDITION
Transmission fluid level and condition should be
checked a minimum of six times per year under nor-
mal operation. If the vehicle is used for commercial
operation, trailer towing, or similar high load opera-
tion, fluid level and condition should be checked
weekly.
Fluid level is checked with the engine running at
curb idle speed, brakes applied, transmission in Neu-
tral, and the transmission fluid at normal operating
temperature (hot).
(1) Transmission fluid must be at normal operat-
ing temperature for accurate fluid level check. Drive
Fig. 9 Park/Neutral Switch Terminals
ZJ
TRANSMISSION AND TRANSFER CASE
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