Today, automatic transmission is a popular and widespread solution. A properly working unit is able to provide a high level of comfort and safety while driving, as well as the presence of an automatic transmission greatly simplifies the process of driving a car.

However, the situation changes in the case when there are certain malfunctions of the automatic transmission. This transmission, depending on the type, can switch jerky, the box kicks, individual gears and modes of operation disappear, the automatic transmission is noisy, vibrates strongly, slams, there is a knock in the automatic transmission when shifting gears, etc

In this article, we will look at what causes the knock when shifting automatic transmission, what in an automatic transmission can knock, as well as how you can localize a separate malfunction by the nature of the knock and noise of the automatic transmission.

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In turn, the JunkCarsUs team would like to draw your attention to the following important point.

Knocking when shifting automatic transmission: the main faults

So, one of the most frequent reasons why car owners with an automatic turn to car services for the purpose of diagnostics are the appearance of noises and knocks in the automatic transmission. Usually, a knock during gear shifting is accompanied by incorrect operation of the unit, but it is not always the case.

In any case, if the driver clearly hears that the automatic transmission knocks, then this is a reason to stop using the vehicle and conduct in-depth diagnostics.

If there is a knock in the automatic transmission, the reasons for the malfunction may be different. The fact is that automatic transmission (especially if we are talking about hydro-mechanical automatic transmission) is a complex unit, which includes many mechanical, hydraulic, and electronic components.

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To identify the source of automatic transmission knock, it is enough to look at the list of frequent faults:

  • Low or high level of transmission oil in the automatic transmission;
  • Improper clearances between the brakes and clutch packs;
  • Valve hang-up in the automatic transmission hydraulic unit or mechatronics;
  • Problems with solenoids, pressure regulator;
  • Malfunction of actuators, automatic transmission ECU;
  • Wear or damage to separate elements in the box;
  • Wear of engine and automatic transmission cushions, etc.

It would seem that there are many reasons, and it is very difficult to localize the knocking in an automatic transmission, and also the knocks in automatic transmission (especially in the case of hydro-mechanical automatic transmission during gear shifting). In practice, however, in a number of cases, it is possible to determine the breakdown by the nature of the knock.

First, during gear shifting in an automatic transmission, the angular acceleration of the output shaft, through which the torque is transmitted, is constant. At the same time, the angular velocity of the pump wheel and turbine wheel in the torque converter changes. Also, the crankshaft of the internal combustion engine rotates at different speeds.