Stall Speed Test

The "Stall" in stall testing occurs when turbine portion of the torque converter is prevented from turning (stalled) by vehicle brakes with vehicle in gear at Wide Open Throttle (WOT). A stall test will reveal the following:

• Slipping clutches, clutch brakes and unidirectionals (one way clutches).
• A freewheeling torque converter stator.
• Weak or poorly tuned engine.

Since stall testing is done with brakes fully locked and zero road speed, it will be possible to test holding/driving power of components responsible for 1st gear in Drive, 3rd, 2nd, 1st and Reverse gear. A stall test will not reveal problems with clutches or clutch brakes specifically responsible for 2nd, 3rd or 4th gear, but by testing 1st and Reverse the following components can be confirmed or eliminated as being a problem:

• "A" clutch that is used in all forward gears.
• "C" clutch that is used in 1st, 2nd, 3rd and Reverse gears.
• Clutch brake No. 3 (CB3) that is used in 1st (gear selector lever position 1) gear.
• Unidirectional No. 2 (UD2) that is used for holding Drive, 3rd and 2nd gear positions.

1. Ensure powertrain is at normal operating temperature and that transmission, coolant and engine oil are topped off. Connect Land Rover Testbook/T4 scan tool or an accurate tachometer. The vehicle tachometer is NOT acceptable for stall testing. Block wheels and apply both hand brake and foot brake firmly. Start engine and place gear selector lever in "D".
2. Depress accelerator to floor and hold until engine speed stabilizes. Release accelerator and record the stall engine speed. DO NOT hold the throttle at WOT for more than 5 seconds. Stall engine speed should be around 2000 RPM. See STALL TEST RESULT  table. Shift into Neutral and hold engine speed at 1000 RPM for 30-60 seconds to cool the transmission fluid. Repeat in 1st gear and record the stall engine speed. Shift into Neutral and hold engine speed at 1000 RPM for 30-60 seconds to cool the transmission fluid. Repeat in Reverse gear and record the stall engine speed.
3. If a stall engine speed of 2400 RPM or greater occurs, the auto gear box control unit will default transmission and illuminate GEARBOX FAULT massage for the driver. A stall speed this high indicates slipping clutches. A torque converter with a seized stator will not show up on a stall test. For stall test result analyses see STALL TEST RESULT  table.