The test consists of determining the critical engine speed with the throttle fully open and the shift lever positions "D" and "R". This test checks the operation of the torque converter stator overrunning clutch and the holding capacity of the gearbox clutches and the low and reverse brake.
Warning: Make sure no one is in front of or behind the vehicle during this test.
1. Check the transmission fluid level. The fluid should be at normal operating temperature (80-90°C). The engine coolant should also be at normal operating temperature (80-90°C).
2. Place chocks under both rear wheels.
3. Connect the tachometer to the engine.
4. Fully apply the parking and service brakes.
5. Start the engine.
6. With the gearshift lever in the "D" position, fully depress the accelerator pedal to lock in maximum engine speed. Do not hold the throttle wide open longer than necessary to obtain maximum engine speed, and never longer than 5 seconds at a time. If more than one test is required, run the engine in neutral at about 1000 rpm for about 2 minutes to cool the transmission fluid between tests.
- Critical rotation speed during testing is 2300-2700 rpm
7. Set the gearshift lever to the "R" position and carry out the test using the above described method.
Critical speed higher than normal at lever position "D"
If the critical speed is higher than normal, there is slippage of the rear clutch or overrunning clutch of the gearbox. In this case, carry out hydraulic tests to determine the cause of slippage.
Critical speed higher than normal at lever position "R"
If the parking critical speed is higher than normal, there is slippage of the front clutch of the transmission or the low and reverse brake. In this case, conduct a hydraulic test to determine the cause of slippage.
Critical rotation speed is below normal in positions "D" and "R"
If the critical speed is below the norm, it is possible to assume that the engine power is insufficient or the torque converter is faulty. Check for misfires in the engine, correct ignition timing, valve clearances, etc. If everything is in order in the engine, the torque converter is faulty.