(3) Have helper start and run engine at 1600 rpm
for test.
(4) Move transmission shift lever four detents rear-
ward from full forward position. This is Reverse range.
(5) Move transmission throttle lever fully forward
then fully rearward and note reading at Gauge
C-3293-SP.
(6) Pressure should be 145 - 175 psi (1000-1207
kPa) with throttle lever forward and increase to 230 -
280 psi (1586-1931 kPa) as lever is gradually moved
rearward.
Test Five - Governor Pressure
This test checks governor operation by measuring
governor pressure response to changes in vehicle
speed. It is usually not necessary to check governor
operation unless shift speeds are incorrect or if the
transmission will not downshift. The test should be
performed on the road or on a hoist that will allow
the rear wheels to rotate freely.
(1) Move 100 psi Test Gauge C-3292 to governor
pressure port.
(2) Move transmission shift lever two detents rear-
ward from full forward position. This is D range.
(3) Have helper start and run engine at curb idle
speed. Then firmly apply service brakes so wheels
will not rotate.
(4) Note governor pressure:
•
Governor pressure should be no more than 20.6
kPa (3 psi) at curb idle speed and wheels not rotating.
•
If pressure exceeds 20.6 kPa (3 psi), a fault
exists in governor pressure control system.
(5) Release brakes, slowly increase engine speed,
and observe speedometer and pressure test gauge (do
not exceed 30 mph on speedometer). Governor pres-
sure should increase in proportion to vehicle speed.
Or approximately 6.89 kPa (1 psi) for every 1 mph.
(6) Governor pressure rise should be smooth and
drop back to no more than 20.6 kPa (3 psi), after
engine returns to curb idle and brakes are applied to
prevent wheels from rotating.
(7) Compare results of pressure test with analysis
chart.
Test Six - Transmission In Overdrive Fourth Gear
This test checks line pressure at the overdrive
clutch in fourth gear range. Use 300 psi Test Gauge
C-3293-SP for this test. The test should be performed
on the road or on a chassis dyno.
(1) Remove tachometer; it is not needed for this test.
(2) Move 300 psi Gauge to overdrive clutch pres-
sure test port. Then remove other gauge and reinstall
test port plug.
(3) Lower vehicle.
(4) Turn OD switch on.
(5) Secure test gauge so it can be viewed from
drivers seat.
(6) Start engine and shift into D range.
(7) Increase vehicle speed gradually until 3-4 shift
occurs and note gauge pressure.
(8) Pressure should be 524-565 kPa (76-82 psi)
with closed throttle and increase to 690-896 kPa
(100-130 psi) at 1/2 to 3/4 throttle. Note that pres-
sure can increase to around 965 kPa (140 psi) at full
throttle.
(9) Return to shop or move vehicle off chassis
dyno.
PRESSURE TEST ANALYSIS CHART
TEST CONDITION
INDICATION
Line pressure OK during
any one test
Pump and regulator
valve OK
Line pressure OK in R
but low in D, 2, 1
Leakage in rear clutch
area (seal rings, clutch
seals)
Pressure low in D Fourth
Gear Range
Overdrive clutch piston
seal, or check ball
problem
Pressure OK in 1, 2 but
low in D3 and R
Leakage in front clutch
area
Pressure OK in 2 but low
in R and 1
Leakage in rear servo
Front servo pressure in 2
Leakage in servo; broken
servo ring or cracked
servo piston
Pressure low in all
positions
Clogged filter, stuck
regulator valve, worn or
faulty pump, low oil level
Governor pressure too
high at idle speed
Governor pressure
solenoid valve system
fault. Refer to diagnostic
book.
Governor pressure low at
all mph figures
Faulty governor pressure
solenoid, transmission
control module, or
governor pressure
sensor
Lubrication pressure low
at all throttle positions
Clogged fluid cooler or
lines, seal rings leaking,
worn pump bushings,
pump, clutch retainer, or
clogged filter.
Line pressure high
Output shaft plugged,
sticky regulator valve
Line pressure low
Sticky regulator valve,
clogged filter, worn pump
DR
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AUTOMATIC TRANSMISSION - 48RE (Continued)
