Test #1
1. To clearly determine the nature of the noise, drive the car on the highway at a speed of approximately 20 km/h.
2. Then gradually increase the speed to 90 km/h, listening simultaneously to different types of noise and noticing the speed at which they appear and disappear.
3. Release the throttle pedal and, without braking, reduce engine speed.
4. When slowing down, pay attention to the change in noise, as well as the moment when the noise increases. Usually, the noise appears and disappears at the same speeds both during acceleration and deceleration.
Warning! Be careful and gentle when turning off the ignition. Do not turn the key more than necessary. This may trigger the anti-theft device.
Test #2
5. Accelerate the car to approximately 100 km/h, put the gearshift lever in neutral, turn off the ignition and allow the car to roll freely until it stops; observe the nature of the noise at different deceleration rates.
6. The noise noticed during the test and corresponding to that noticed during the first test does not come from the final drive gears, since they cannot produce noise without a load.
7. Conversely, noise noted in the first test and not repeated in the second may come from the gearbox gears or the bearings of the pinion or differential.
Test #3
8. With the vehicle stationary and braked, turn on the engine and, gradually increasing its speed, compare the noises that arise with those noted in the previous tests. Noises that are similar to the noises of test No.1 will indicate that they are not the noise of the gearbox in test No.1 and are caused by other units.
Test #4
9. The noises detected during the first test and not repeated during subsequent tests come from the gearbox; to confirm, lift the rear wheels, start the engine and engage fourth gear. This will ensure that the noise is indeed coming from the gearbox and not from other components, such as the suspension or body.