Dodge D150 1990 Service Manual page 904

• AUTOMATIC TRANSMISSION 21 - 53
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 a tachometer t o t h e engine.
(2) Check and adjust transmission fluid level.
(3) Start a n d r u n t h e engine u n t i l transmission
fluid reaches n o r m a l operating temperature.
(4) Block the front wheels.
(5) F u l l y apply the service a n d p a r k i n g brakes.
(6) Open t h e t h r o t t l e completely for no more t h a n
five seconds and record m a x i m u m engine r p m regis-
tered on the tachometer.
CAUTION: Stall testing causes a rapid increase in
transmission fluid temperature. Do not hold the
throttle open any longer than five seconds. 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) I f engine speed exceeds m a x i m u m shown i n the
s t a l l speed chart, release t h e accelerator i m m e d i -
ately. This indicates t h a t transmission c l u t c h slip-
page is occurring.
(8) Shift t h e transmission i n t o N e u t r a l . Operate
t h e engine for 20 seconds. Stop t h e engine, shift t h e
transmission i n t o P a r k and release t h e brakes.
(9) Stall speeds should be: 1800-2100 r p m w i t h
3.9L engine a n d 1700-2000 r p m w i t h 5.2L/5.9L en-
gines.
(10) Refer t o S t a l l Test Diagnosis.
STALL TEST DIAGNOSIS
Stall Speed Too High
I f the stall speed exceeds specifications b y more
t h a n 200 r p m , transmission c l u t c h slippage i s i n d i -
cated.
Stall Speed Too Low
Low stall speeds w i t h a properly t u n e d engine i n -
dicate a torque converter o v e r r u n n i n g c l u t c h prob-
l e m . The condition should be confirmed b y road
t e s t i n g prior to converter replacement.
The converter o v e r r u n n i n g c l u t c h is s l i p p i n g when:
S t a l l speeds are 250 t o 350 r p m below specified m i n -
i m u m and t h e vehicle operates properly a t h i g h w a y
speeds but has poor l o w speed acceleration.
Stall Speed Normal
I f stall speeds are n o r m a l b u t a b n o r m a l t h r o t t l e
opening is required t o m a i n t a i n h i g h w a y speeds, t h e
converter o v e r r u n n i n g c l u t c h is seized and the torque
converter m u s t be replaced.
Converter Noise During Test
A w h i n i n g noise caused b y fluid flow is n o r m a l
d u r i n g a s t a l l test. However, loud metallic noises i n -
dicate a damaged converter. To confirm t h a t noise is
o r i g i n a t i n g from the converter, operate the vehicle at
l i g h t t h r o t t l e i n D r i v e a n d N e u t r a l o n a hoist a n d lis-
t e n for noise coming from t h e converter housing.
AIR PRESSURE TEST
A i r pressure t e s t i n g can be used t o check clutch
and band operation w i t h t h e transmission either i n
the vehicle, or o n t h e w o r k bench as a final check af-
ter overhaul.
A i r pressure t e s t i n g requires t h a t t h e o i l p a n and
valve body be removed from t h e transmission. The
servo a n d c l u t c h apply passages are shown i n Figure
5. ' " • •
FRONT SERVO APPLY,
REAR SERVO APPLY
LINE PRESSURE TO!
ACCUMULATOR
GOVERNOR
PRESSURE
FRONT
SERVO
.RELEASE
PUMP
SUCTION
PUMP
PRESSURE
FRONT
CLUTCH
APPLY
REAR
CLUTCH
APPLY
TO TORQUE
CONVERTOR
/
FROM TORQUE
CONVERTER
TO
GOVERNOR
TO COOLER
Fig. 5 Air Pressure Test Passages
Front Clutch Test
Place one or t w o fingers on the clutch housing and
apply a i r pressure t h r o u g h front clutch apply passage
(Fig. 5). Piston movement can be felt and a soft t h u d
heard as t h e c l u t c h applies.
Rear Clutch Test
Place one or t w o fingers on the clutch housing and
apply a i r pressure t h r o u g h rear clutch apply passage
(Fig. 5). P i s t o n movement can be felt and a soft t h u d
heard as t h e c l u t c h applies.
Front Servo Test
A p p l y a i r pressure t o the front servo apply passage.
The servo r o d should extend and cause t h e band to