Troubleshooting is carried out in the following order.
Test 1. To clearly determine the nature of the noise, drive the car on the highway at a speed of approximately 20 km/h. Then gradually increase the speed up to 90 km/h, listening at the same time for different types of noise and noticing the speed at which they appear and disappear.
Release the throttle pedal and, without braking, dampen the engine speed.
While decelerating, watch for changes in the noise as well as when the noise gets louder. Normally, the noise comes and goes at the same speeds both when accelerating and when decelerating.
Test 2. Accelerate the vehicle to approximately 100 km/h, place the gear lever in neutral, and allow the vehicle to roll freely to a stop; watch the noise pattern at different deceleration rates.
The noise, which is dependent on the manipulation of the accelerator pedal, comes from the main pair.
Bearings can also make noise in the freewheel: with «hissing» And «rumble» bearings of the drive gear are noisy, and the low-frequency «rumble» produce bearings for differential and axle shafts.
Test 3. With the car stationary and braked, turn on the engine and, gradually increasing its speed, compare the noises that have arisen with those seen in previous tests. Noises found to be similar to Test 1 will indicate that they are not gearbox noise and are caused by other components.