Jeep 1996 Grand Cherokee Service Manual - page 1154
CONVERTER STALL TEST
Stall
testing
involves
determining
maximum
engine speed obtainable at full throttle with the rear
wheels locked and the transmission in D range. This
test checks the holding ability of the converter over-
running and transmission clutches. When stall test-
ing is completed, refer to the stall speed chart and
diagnosis guides.
WARNING:
NEVER ALLOW ANYONE TO STAND
DIRECTLY IN LINE WITH THE VEHICLE FRONT OR
REAR DURING A STALL TEST. ALWAYS BLOCK
THE WHEELS AND FULLY APPLY THE SERVICE
AND PARKING BRAKES DURING THE TEST.
STALL TEST PROCEDURE
(1) Connect tachometer to engine. Position tachom-
eter so it can be viewed from driver’s seat.
(2) Check transmission fluid level. Add fluid if nec-
essary.
(3) Drive vehicle to bring transmission fluid up to
normal operating temperature. Vehicle can be driven
on road, or on chassis dynamometer, if available.
(4) Block front wheels.
(5) Fully apply service and parking brakes.
(6) Open throttle completely and record maximum
engine speed registered on tachometer. It takes 4-10
seconds to reach max rpm. Once max rpm has
been achieved, do not hold wide open throttle
for more than 4-5 seconds.
CAUTION:
Stalling the converter causes a rapid
increase in fluid temperature. To avoid fluid over-
heating, hold the engine at maximum rpm for no
more than 5 seconds. If engine exceeds 2500 rpm
during the test, release the accelerator pedal imme-
diately; transmission clutch slippage is occurring.
(7) If a second stall test is required, cool down
fluid before proceeding. Shift into NEUTRAL and run
engine at 1000 rpm for 20-30 seconds to cool fluid.
(8) Refer to Stall Test Analysis.
STALL TEST ANALYSIS
Stall Speed Too High
If the stall speed exceeds 1800-2300 rpm by more
than 200 rpm, transmission clutch slippage is indi-
cated.
Stall Speed Low
Low stall speed with a properly tuned engine indi-
cate a torque converter overrunning clutch problem.
The condition should be confirmed by road testing
before
to
converter
replacement. A stall
speed
250-350 rpm below normal indicates the converter
overrunning clutch is slipping. The vehicle also
exhibits poor acceleration but operates normally once
highway cruise speeds are reached. Torque converter
replacement will be necessary.
Stall Speed Normal But Acceleration Poor
If stall speeds are normal (1800-2300 rpm) but
abnormal throttle opening is required for accelera-
tion, or to maintain cruise speed, the converter over-
running clutch is seized. The torque converter will
have to be replaced.
Converter Noise During Test
A whining noise caused by fluid flow is normal dur-
ing a stall test. However, loud metallic noises indi-
cate a damaged converter. To confirm that noise is
originating from the converter, operate the vehicle at
light throttle in DRIVE and NEUTRAL on a hoist
and listen for noise coming from the converter hous-
ing.
Fig. 13 Pressure Test Analysis
ZJ
TRANSMISSION AND TRANSFER CASE
21 - 15
DIAGNOSIS AND TESTING (Continued)