TM 9-2320-266-34
(Z) Connect a 100 psi gage to the governor pressure
(5) The line pressure should read 54 to 60 psi with the
take-off point, located at the lower left side of the extension
throttle lever forward and should gradually increase, as the
near the mounting flange (figure 4-11).
lever is moved rearward, to 90 to 96 psi.
(2) Operate the transmission in third gear to read the
(6) The lubrication pressure should be 5 to 15 psi with
pressures, and compare speeds shown in table 4-2. If gov-
the lever forward, and 10 to 30 psi with the lever rearward.
ernor pressures are incorrect at the given vehicle speeds, the
This tests the pump output, pressure regulation, and the con-
governor valve and/or weights are probably sticking (see
dition of the rear clutch and the lubrication hydraulic
circuits.
to changes in mph and should return to 0 to 1-1/2 psi when
c. Test Three (Selector in "D").
the vehicle is stopped. High pressure at standstill (above
(1) Attach a 100 psi gage to the line and front servo
2 psi) will prevent the transmission from downshifting.
release ports.
i. Throttle Pressure. No gage port is provided for the
(2) Operate the engine at 1,000 rpm.
throttle pressure. If part-throttle upshift speeds are delayed
or occur too early in relation to vehicle speeds, you have in-
(3) Move the selector lever on the transmission two
correct throttle pressure. Engine runaway on either upshifts
detents back from the full forward position ("D" position).
or downshifts can also indicate incorrect (low) throttle pres-
(4) Read the pressures on both gages as the throttle
sure setting. The throttle pressure must not be adjusted until
lever on the transmission is moved from the full forward
the transmission throttle linkage adjustment is correct,
position to the full rearward position.
4-5. Converter Stall Test.
(5) The line pressure should read 54 to 60 psi with
the throttle lever forward, and should gradually increase as
the lever is moved rearward, to 90 to 96 psi.
During the test, don't let anyone stand in
(6) The front servo release is pressurized only in direct
front of the vehicle. If the brakes fail or
drive and should be within 3 psi of the line pressure, up to
are released. the truck will move forward.
the downshift point. This tests the pump output, pressure
regulation, and the condition of the rear clutch and the front
The stall test determines the engine speed at full throttle
clutch hydraulic circuits.
in the "D" position. This test checks the torque converter
f. Test Four (Selector in Reverse).
stator clutch operation, and the holding ability of the trans-
mission clutches. Check the transmission oil level and bring
(1) Attach a 300 psi gage to the rear servo apply port.
the engine to normal operating temperature before the stall
(2) Operate the engine at 1,600 rpm.
operation. Both the parking and service brakes must be fully
(3) Move the selector lever on the transmission four
applied, and the front wheels blocked while making this test.
detents back from the full forward position ("R" position).
Do not hold the throttle open any longer than is necessary to
This tests the pump output, pressure regulation, and the con-
get a maximum engine speed reading, and never longer than
dition of the front clutch and the rear servo hydraulic
5 seconds at a time. If more than one stall check is re-
circuits.
quired, operate the engine at approximately 1,000 rpm in
Neutral to cool the transmission fluid between runs. If the
(4) Move the selector lever on the transmission two
engine speed exceeds the maximum limits, it indicates trans-
detents back from the full forward position ("D" position),
mission clutch slippage; release the accelerator immediately.
to check that the rear servo pressure drops to zero. This
tests for leakage into the rear servo, caused by case porosity,
Stall Speed A hove 2,150 rpm. If the stall speed ex-
Q.
which in turn causes reverse band burn out.
ceeds 2,150 rpm, transmission clutch slippage is indicated.
Follow the transmission oil pressure and air pressure checks
g. Test Result Indications.
outlined in paragraph 4-6 to determine the cause of slippage.
(1) If proper line pressure, minimum to maximum, is
b. Stall Speed Below 1,450 rpm. Low stall speeds with a
found in any one test, the pump and pressure regulator are
properly tuned engine indicate torque converter stator clutch
working properly.
problems. A road test will be necessary to identify the ex-
(2) Low pressure in "D," "1 ," and "2," but correct
act problem.
pressure in "R" indicates a rear clutch circuit leakage.
(1) If the stall speeds are below 1,450 rpm, and the
(3) Low pressure in "D" and "R," but correct pressure
vehicle operates properly at highway speeds, but has poor
in "1" indicates a front clutch circuit leakage.
through-gear acceleration, the stator overrunning clutch is
slipping. Replace the torque converter.
(4) Low pressure in "R" and " 1," but correct pressure
in "2" indicates a rear servo circuit leakage.
(2) If the stall speed and acceleration are normal, but
abnormally high throttle opening is required to maintain
(5) Low line pressure in all positions indicates a de-
highway speeds, the stator clutch has seized. Replace the
fective pump, a clogged filter, or a stuck pressure regulator
torque converter.
valve.
c. Noise. A whining or siren-like noise due to fluid flow
h. Governor Pressure. Test this only if the transmission
is normal during stall operation with some converters.
shifts at the wrong vehicle speeds when the throttle rod is
However, loud metallic noises from loose parts or inter-
correctly adjusted.
4-14
