The breather cap must be free of dirt and free to rotate.
We apply a force of about 10 kgf along the axis of the suspended wheel with our hands and determine the presence of axle play. It is allowed no more than 0.7 mm. The parking brake must be released during this test.
Minor oil leakage allowed (sweating) from under the cuff of the front bearing of the final drive, but with strong oiling of the gearbox and the bottom of the car above the main gear, the cuff should be replaced.
Determine the noise in the rear axle and, accordingly, the need for repair can be based on the results of the following tests.
Test 1. We smoothly accelerate the car on a flat road from a speed of 20 to 90 km / h. At the same time, we listen to the noise and notice the speed at which it appears and disappears.
Release the pedal «gas» and listen to the car in engine braking mode. Usually the noise comes on and off at the same speeds, both when accelerating and when decelerating.
Test 2. We accelerate the car to a speed of 100 km / h, move the gear 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 rates.
Attention! Be careful when turning off the ignition. Do not turn the key more than necessary to turn off the ignition, as in position «parking» (when the key is removed from the lock) the anti-theft device may operate and the steering wheel may be locked.
In the first version, we tested the gearbox in the acceleration and deceleration mode under the load created by the engine. In the second - without it. If the sound is present only during the first test, the cause may be the gears of the gearbox, bearings of the drive gear or differential. If the noise appears in both cases, its source must be sought elsewhere.
Test 3. We set the gear lever to the neutral position, start the engine and gradually increase the speed of the crankshaft. Compare the resulting noises with those seen earlier. If they are similar to the noises from the first test, this indicates that they are not coming from the gearbox.
Test 4. Noises found on the first test and not on subsequent tests are caused by the gearbox. To confirm, we raise the rear wheels, start the engine and turn on the fourth gear. We make sure that the noise really comes from the gearbox, and not from other components or parts.