11
b.
Transmission Stall Test Procedure
The engine stall point (rpm) under load is compared to the engine manufacturer’s
specified rpm for the stall test.
• Connect a tachometer of known accuracy to the engine, and install a
temperature probe into the converter-out (to cooler) line. Bring the
transmission to the normal operating temperature of 180–220°F (82–104°C).
• With the vehicle securely blocked and the parking brake and service brake
applied, shift to any forward range. Then, accelerate the engine to wide-open
throttle and record the maximum rpm the engine will attain. (This test may
also be conducted in R (Reverse) range if necessary.)
• Reduce engine speed to idle and shift to N (Neutral) or P (Park).
WARNING: When conducting a stall test, the vehicle must be
positively prevented from moving. Apply the parking brake and
service brake, and block the vehicle securely. Warn personnel to keep
clear of the vehicle and its travel path. Failure to do so can cause
serious injury.
CAUTION: Never maintain the stall condition for more than 30
seconds at any one time because of the rapid rise in fluid temperature.
Do not let the converter-out fluid temperature exceed 300°F (149°C).
Do not rely on converter-out fluid temperature to limit stall duration.
During stall conditions, internal temperatures rise much faster than
converter-out fluid temperature. Run the engine at 1200–1500 rpm for
two minutes to cool the transmission fluid between tests. If the stall
test is repeated, do not let the engine overheat.
NOTE: Some engines have smoke controls and throttle-delay
mechanisms. These engines require the following stall test procedure:
Put the transmission in the first range hold position. Operate the
vehicle at maximum speed in first range. Apply the vehicle brakes
while maintaining full throttle. As soon as the vehicle is completely
stopped, read the engine rpm (stall speed) from the tachometer.
Reduce engine speed to idle and shift to N (Neutral) or P (Park).
Increase engine speed to cool the torque converter.
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