The breather cap must be free of dirt and rotate freely.
We apply a force of about 10 kgf along the axis of the suspended wheel with our hands and determine the presence of play in the axle shaft. It is allowed to be no more than 0.7 mm. The parking brake must be released during this check.
Minor oil leakage is allowed (sweating) from under the front bearing seal of the main gear, but if the gearbox and the bottom of the car above the main gear are heavily oiled, the seal should be replaced.
The noise in the rear axle and, accordingly, the need for repair can be determined based on the results of the following tests.
Test 1. Smoothly accelerate the car on a flat road from 20 to 90 km/h. At the same time, listen to the noise and notice the speed at which it appears and disappears.
We release the gas pedal and listen to the car in engine braking mode. Usually the noise appears and disappears at the same speeds, both during acceleration and deceleration.
Test 2. We accelerate the car to a speed of 100 km/h, move the gearshift lever to neutral, turn off the ignition and roll freely to a stop. At the same time, we monitor the nature of the noise at various deceleration speeds.
Warning! Be careful when turning off the ignition. Do not turn the key more than necessary to turn off the ignition, since in the "parking" position (when the key is removed from the lock) the anti-theft device may be activated and the steering wheel may be locked.
In the first variant, we tested the gearbox in acceleration and braking mode under the load created by the engine. In the second variant, without it. If the noise is present only during the first test, it may be caused by the gearbox gears, the bearings of the drive gear or the differential. If the noise appears in both cases, its source should be sought elsewhere.
Test 3. We set the gearbox lever to neutral, start the engine and gradually increase the crankshaft speed. We compare the noises that arise with those noticed earlier. If they are similar to the noises that arose during the first test, this indicates that they do not come from the gearbox.
Test 4. The noises detected during the first test and absent during subsequent tests are caused by the gearbox. To confirm, we lift the rear wheels, start the engine and engage fourth gear. We make sure that the noises really come from the gearbox and not from other units or parts.