JEEP CHEROKEE 1995 Service Repair Manual

CONVERTER STALL TEST
Stall testing involves determining maximum engine
rpm obtainable at full throttle with the rear wheels
locked and the transmission in D range. This test
checks the holding ability of the converter overrun-
ning clutch and both of the transmission clutches.
When stall testing is completed, refer to the Stall
Speed Specifications chart and Stall Speed Diagnosis
guides.
WARNING: NEVER ALLOW ANYONE TO STAND IN
FRONT OF THE VEHICLE DURING A STALL TEST.
ALWAYS BLOCK THE FRONT WHEELS AND APPLY
THE SERVICE AND PARKING BRAKES DURING
THE TEST.
STALL TEST PROCEDURE
(1) Connect tachometer to engine.
(2) Check and adjust transmission fluid level.
(3) Start and run engine until transmission fluid
reaches normal operating temperature.
(4) Block front wheels.
(5) Fully apply service and parking brakes.
(6) Open throttle completely and record maximum
engine rpm registered on tachometer. It will take
from 3 to 10 seconds to reach maximum rpm. How-
ever, once maximum rpm has been achieved,do not
hold wide open throttle for more than 5 sec-
onds.
CAUTION: Stalling the converter causes a rapid in-
crease in fluid temperature. To avoid fluid overheat-
ing, hold wide open throttle for no more than 5
seconds after reaching peak rpm. In addition, if
more than one stall test is required, run the engine
at 1000 rpm with the transmission in Neutral for at
least 20 seconds to cool the fluid.
(7) Stall speeds should be in 1700-2150 rpm range.
CAUTION: If engine exceeds 2150 rpm, release ac-
celerator pedal immediately as transmission clutch
slippage is occurring.
(8) Shift transmission into Neutral. Run engine for
20-30 seconds at 1000 rpm to cool fluid. Then stop
engine, shift transmission into Park and release
brakes.
(9) Refer to Stall Test Diagnosis.
STALL TEST DIAGNOSIS
Stall Speed Too Low
Low stall speeds with a properly tuned engine in-
dicate a torque converter overrunning clutch prob-
lem. The condition should be confirmed by road
testing prior to converter replacement.The converter overrunning clutch is slipping when
stall speeds are 250 to 350 rpm below specified min-
imum.
A converter overrunning clutch failure will result
in sluggish acceleration in all speed ranges. It will
also require greater than normal throttle opening to
maintain cruising speeds.
Stall Speed Too High
If stall speed exceeds 2150 rpm, transmission
clutch slippage is occurring.
Stall Speed Normal But Acceleration Is Sluggish
If stall speeds are within specified range but abnor-
mal throttle opening is required for acceleration, or
to maintain cruise speeds, the converter overrunning
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 lis-
ten for noise from the converter housing.
AIR PRESSURE TEST
Air pressure testing can be used to check clutch
and band operation with the transmission either in
the vehicle, or on the work bench as a final check af-
ter overhaul.
Air pressure testing requires that the oil pan and
valve body be removed from the transmission.
The servo and clutch apply passages are shown in
Figure 8.
Air Test Procedure
(1) Place one or two fingers on the clutch housing
and apply air pressure through front clutch apply
passage (Fig. 8). Piston movement can be felt and a
soft thud heard as the clutch applies.
(2) Place one or two fingers on the clutch housing
and apply air pressure through rear clutch apply
passage (Fig. 8). Piston movement can be felt and a
soft thud heard as the clutch applies.
(3) Apply air pressure to the front servo apply pas-
sage. The servo rod should extend and cause the
band to tighten around the drum. Spring tension
should release the servo when air pressure is re-
moved.
(4) Apply air pressure to the rear servo apply pas-
sage. The servo rod should extend and cause the
band to tighten around the drum. Spring tension
should release the servo when air pressure is re-
moved.
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CONVERTER HOUSING LEAK DIAGNOSIS
Two items must be established when diagnosing
leaks from the converter housing area. First, it must
be verified that a leak condition actually exists. And
second, the true source of the leak must be deter-
mined.
Some suspected converter housing fluid leaks may
not be leaks at all. Residual fluid in the housing, or
excess fluid spilled during factory fill or refill after
repair can be mistaken for a leak. In addition, a rear
main seal leak can also be mistaken for a pump seal
leak if care is exercised.
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. Pump O-ring or
pump body leaks follow the same path as a seal leak
(Fig. 9).
Pump vent or pump attaching bolt leaks are gener-
ally deposited on the inside of the converter housing
and not on the converter itself (Fig. 9).
Pump seal or gasket leaks usually travel down the
inside of the converter housing.
Front band lever pin plug leaks are generally de-
posited on the housing and not on the converter.
LEAK DIAGNOSIS PROCEDURE
(1) Raise the rear of the vehicle and allow accumu-
lated fluid to drain out of the converter housing.
(2) Check and adjust the transmission fluid level.
(3) Raise the vehicle. Remove the converter hous-
ing dust cover and wipe as much fluid as possible
from the converter housing.(4) Fabricate a test probe (Fig. 10). Then attach
the probe to the converter housing with one of the
dust shield bolts (Fig. 10).
(5) Have a helper run the engine at 2500 rpm
(with the transmission in Neutral) for two minutes;
then stop the engine.
(6) Inspect the test probe and converter housing. If
a leak is evident, note the color of the fluid. Trans-
mission fluid is red. Engine oil ranges in color from
brown to green, or to black when the oil is dirty.
(7) If the probe upper surface is dry, the converter
and seal are not at fault. A path of fluid across the
probe upper surface indicates a converter or seal
leak. Fluid leakingunderthe probe is coming from
the pump housing area (Fig. 11).
(8) Fluid leaking under the probe could be from
the: pump seal and/or bushing, pump vent, kickdown
lever shaft access plug, pump bolts, or porous spots
in the pump body or transmission case (Fig. 11).
(9) If porous spots in the transmission case or
pump body are the suspected leak source, pressurize
the transmission as described in Leak Testing With
Air Pressure.
Fig. 8 Air Pressure Test Passages
Fig. 9 Typical Converter Housing Leak Paths
Fig. 10 Leak Test Probe
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LEAK TESTING WITH AIR PRESSURE
This test involves closing off the transmission open-
ings and pressurizing the transmission to 8 psi with
Air Pump Tool 7700.
A soapy water solution is applied to suspected leak
points before and during the pressure test. Leaks will
be indicated by the presence of air bubbles coming
through the solution.
Some transmission openings such as the fill tube
and front cooler line fitting can be closed off with a
rubber plug or similar device. Plugs can secured with
wire or duct tape.
The transmission rear output shaft opening is
closed off simply by leaving the transfer case bolted
in place. However, if the transfer case has been re-
moved, a shipping plug can used to close off this
opening.
The torque converter hub opening in the pump and
the pump vent require special tools to close them off.
The converter hub seal cap is made from thin wall
tube anda3mm(1/8 in.) thick disc (Fig. 12). A re-
taining strap is needed to secure the seal cup for
testing. The strap can be made from 32 mm (1-1/4
in.) wide stock (Fig. 13). The strap attaching hole po-
sitions are approximate only. Measure hole position
on the converter housing before drilling.
The pump vent tool is made from 6 mm (1/4 in.)
rod and 5 mm (3/16 in.) plate (Fig. 14). The fabri-
cated tools can all be made from mild steel or alumi-
num stock.
AIR PRESSURE LEAK TEST PROCEDURE
(1) Install vent plug, converter hub seal cup and
cup retaining strap (Fig. 15).
(2) Close off remaining transmission openings with
rubber plugs, or stoppers.Do not close off rear
cooler line fitting. Air pump will be attached to
this fitting.(3) Attach Air Pump 7700 to rear cooler line fit-
ting. Connect length of copper tube to fitting. Then
attach air pump hose to tube with hose clamp (Fig.
16).
Fig. 11 Pump Area Inspection PointsFig. 12 Converter Hub Seal Cup
Fig. 13 Seal Cup Retaining Strap
Fig. 14 Pump Vent Plug
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(4) Apply thick soapy water solution to suspected
leak areas.
CAUTION: The recommended test pressure is 8 psi.
The maximum allowable test pressure is 10 psi. Do
not exceed specified test pressure.
(5) Pressurize transmission to 8 psi with air pump.
(6) Observe suspected leak areas. Air bubbles ap-
pearing in soapy water solution indicate leak points.
(7) Remove test tools and plugs after test comple-
tion and make necessary repairs as described in Leak
Correction procedure.
CONVERTER HOUSING AREA LEAK
CORRECTION
(1) Remove converter.
(2) Tighten front band adjusting screw until band
is tight around clutch retainer. This prevents
clutches from coming out when oil pump is removed.
(3) Remove oil pump and seal. Inspect pump hous-
ing drainback and vent holes for obstructions. Clear
holes with solvent and wire.(4) Inspect pump bushing and converter hub. If
bushing is scored, replace it. If converter hub is
scored, either polish it with crocus cloth or replace
converter if scoring is severe.
(5) Install new pump seal, O-ring, gasket, bushing.
Replace oil pump if cracked, porous or damaged in
any way.
(6) Loosen kickdown lever pin plug two turns. Ap-
ply Permatex No. 2 or equivalent to plug threads and
tighten plug to 17 Nzm (150 in-lbs) torque.
(7) Adjust front band.
(8) Lubricate pump seal and converter hub with
transmission fluid or petroleum jelly and install con-
verter.
(9) Install transmission.
(10) Install converter housing dust shield and
lower vehicle.
DIAGNOSIS GUIDES AND CHARTS
The diagnosis charts provide additional reference
for transmission and converter clutch diagnosis.
The hydraulic flow charts outline fluid flow and hy-
draulic circuitry. Circuit operation is provided for all
gear ranges. Normal working pressures are also sup-
plied for each of the various gear ranges.
Fig. 15 Vent Plug And Hub Seal Cup Installation
Fig. 16 Pressurizing Transmission
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