Symptom: a 4.2L Touareg slow process in the right rear wheel abnormal sound. And the customer has been reflected in this before have been to a lot of maintenance plant, check the results of different opinions, some think there are problems with the transfer device, and some think the rear axle differential failure, but in the replacement parts or other methods after maintenance diagnosis Failure still can not be ruled out.
    Troubleshooting: As the fault occurred in the process of driving, so the first road test, in a variety of speed are no abnormal phenomenon. Only start the engine in the parked state. Then loose the pedal (either in D or manual mode). Do not continue to step on the accelerator pedal to speed, to maintain idle speed and speed in the 5km / h under the slow straight, then you can clearly hear the rhythm under the chassis issued a "slightly deng" sound, and accompanied by a sense of vibration. There was no sound in the turn. More than the above speed when no abnormal sound.
    Carry on the car. A, S5051B fault guidance, and no relevant fault code exists. And check all the transmission parts, ball, rubber pad no problem. Is there a problem with the splitter motor? Try to replace a motor. The fault still exists. At the same time, it was observed that the tires of the car were inconsistent. Doubt whether the resulting failure. Immediately transposition the tire, but after the re-test the fault still exists. And the driving mode in the "LOW" or differential lock lock when there is no sound of vibration. Try to unplug the harness connector of the splitter motor. The fault disappears.
    Check again. Found before and after the tires in addition to patterns, different brands outside Other sizes are the same. For the sake of insurance, measure the actual size of the outer diameter of the front and rear wheels. The result is surprising. Two rounds of the height of the ground even a difference of up to 2cm. Describe tires of the same size but different brands. Although the outer diameter of the hub is the same. But because of the rubber pattern and the thickness of the different tire diameter is likely to vary greatly. And the tire diameter size is likely to make four-wheel drive vehicles before and after the bridge to produce different wheel speed. In a full-time four-wheel drive, the drive torque is evenly distributed to the front and rear axles without a slip between the axles. If the axle differential lock sensor of the splitter control unit detects the presence of the axle The speed difference will be calculated by the control unit torque difference. And adjust the diaphragm clutch through the stepper motor to apply the required pressure. To ensure that the front axle axle without slip generated. Based on the above reasons, the car replaced the same brand of the same specifications of the tire to continue road test, failure disappeared.