Torque Converter Stall Test
To perform a stall test, install a tachometer, chock all four wheels, and set the parking brake. Make sure the tachometer is viewable from the driver's seat. Place your foot firmly on the brake pedal, and place the transmission's shift selector in Drive. While holding the brake pedal, press and hold the throttle pedal to the floor for 2 or 3 seconds. Always check with the manufacturer's recommendations because the test stresses the transmission. Never exceed 5 seconds. Compare the tachometer reading (stall speed) to the manufacturer's specifications.
If the torque converter stator's one-way clutch is slipping, a torque converter stall test should be performed before bench testing the converter. Always check with the vehicle's manufacturer before performing this test. Do not allow the transmission fluid to exceed 174° F. During a stall test, ensure no one stands in front of or behind the vehicle.
During a stall test, the torque converter's impeller spins at maximum speed while the turbine is stationary. Since everything from the turbine back is stationary, an out-of-balance driveshaft or tire would not appear during a stall test. An out-of-balance driveshaft causes a vibration that increases with vehicle speed, not while it sits stationary.