Jeep Wrangler 1997, Manual

Page: 986 / 1152

Clutch/Band Application
The front/rear clutch pistons and servo pistons are
actuated by line pressure. When line pressure is
removed, the pistons are released by spring tension.
On 2-3 upshifts, the front servo piston is released
by spring tension and hydraulic pressure. The accu-
mulator controls hydraulic pressure on the apply side
of the front servo during 1-2 upshifts and at all
throttle openings.
CONVERTER CLUTCH ENGAGEMENT
Converter clutch engagement in third gear is con-
trolled by sensor inputs to the powertrain control
module. Inputs that determine clutch engagement
are: coolant temperature, vehicle speed and throttle
position. The torque converter clutch is engaged by
the clutch solenoid on the valve body. The clutch will
engage at approximately 56 km/h (35 mph) with light
throttle, after the shift to third gear.
CONVERTER DRAINBACK VALVE
The drainback valve is located in the transmission
cooler outlet (pressure) line. The valve prevents fluid
from draining from the converter into the cooler and
lines when the vehicle is shut down for lengthy peri-
ods. Production valves have a hose nipple at one end,
while the opposite end is threaded for a flare fitting.
All valves have an arrow (or similar mark) to indi-
cate direction of flow through the valve.
BRAKE TRANSMISSION SHIFT INTERLOCK
MECHANISM
The Brake Transmission Shifter/Ignition Interlock
(BTSI), is a cable and solenoid operated system. It
interconnects
the automatic transmission floor
mounted shifter to the steering column ignition
switch (Fig. 3). The system locks the shifter into the
PARK position. The Interlock system is engaged
whenever the ignition switch is in the LOCK or
ACCESSORY position. An additional electrically acti-
vated feature will prevent shifting out of the PARK
position unless the brake pedal is depressed at least
one-half an inch. A magnetic holding device in line
with the park/brake interlock cable is energized
when the ignition is in the RUN position. When the
key is in the RUN position and the brake pedal is
depressed, the shifter is unlocked and will move into
any position. The interlock system also prevents the
ignition switch from being turned to the LOCK or
ACCESSORY position (Fig. 4) unless the shifter is
fully locked into the PARK position.
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.
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.
21 - 80 TRANSMISSION AND TRANSFER CASE
TJ
DESCRIPTION AND OPERATION (Continued)