What is an automatic transmission hydraulic unit and how it works

Hydraulic Transmissions

The automatic transmission hydraulic unit, what is it? The hydraulic valve plate is designed to control the clutch clutches. The assembly ensures the smooth operation of the automatic transmission.

Why do hydroblocks break down? The valve control plate fails with mechanical wear, as the automatic transmission hydraulic unit is under constant load. The causes of breakdowns: Poor maintenance; Improper operation; Failure of the cooling system; Untimely change of transmission fluid; Overheating of the automatic transmission; Oxidation of contacts.

During operation the valves often become dirty and fail. Washing the automatic transmission’s hydraulic unit will help to eliminate the problem. Another problem of automatic transmissions is the wear of the spring. The failure is detected with a special high-precision tool. Dirt and friction materials can destroy the transmission. We do not recommend cleaning the automatic transmission hydroblock by yourself. For qualitative removal of dirt and wear products, special devices and tools are required. How to determine if the control unit is not working? Signs of the automatic transmission hydraulic unit malfunction: Vibrations; Grinding; Slipping; Jerks and pushing when shifting gears.

Diagnostics will help to determine the exact cause of the breakdown. A computer is connected to the mechanism and all the necessary tests are performed. Features of repair If the box strongly hums and badly shifts gears, do not rush to buy an automatic transmission hydroblock. Go for diagnosis. Do not try to determine the breakdown on your own. Trust the experts. Repair is performed in stages: Visual inspection; Full diagnosis; Removal; Disassembly; Flushing of the automatic transmission hydraulic unit; Replacement of parts; Assembly.

The part is washed in a special solvent. The part is cleaned with a brush. Chips, dust and other contaminants are removed. Then the unit is dried with compressed air. Useful tips for car owners Preventive measures will help to prevent breakdowns and avoid repair of automatic transmission units. Carefully monitor the condition of the automatic transmission cooling system. Observe the rules of operation. In winter you should not start driving in a car with an unheated automatic transmission. Check the oil level in the gearbox regularly. Use only high-quality transmission fluid. Change oil and filters in a timely manner. We carry out repair of automatic transmission hydraulic unit on the professional equipment. We use original auto parts from reliable manufacturers. If after the repair you can not restore the transmission, order the hydroblock. In our store we have all the necessary parts. Selecting accessories is easy and simple. Find out the price of an automatic transmission hydroblock and order the part through the online application. The cost will depend on the make of the car The automatic transmission hydroblock ensures the effective operation of clutches and friction clutches. The unit consists of channels, valves and sensors responsible for shifting gears. Causes and signs of hydroblock malfunction If you hear a strange knocking in the box when shifting gears, go to our car service. Sharp shocks in the transmission require repair of the automatic transmission hydraulic unit. The causes of breakdowns: overheating of the automatic box; untimely oil change; contamination of the valves; breakdown of the solenoids; wear and tear of the consumables.

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To avoid repairing the automatic transmission’s hydroblock, perform regular maintenance of the automatic transmission. Clean all components from dirt in time. In the car service center before repair, the device is scanned. They reveal all the defects in the operation of the unit. Decipher and eliminate error codes. Masters perform: diagnostics, cleaning and replacement of solenoids, disassembly, flushing, restoration of the valve block, calibration, assembly, run-in.

Depending on the wear of the automatic transmission, repair or replacement of the hydroblock is performed. Choose a suitable repair kit For the convenience of overhaul of automatic transmission hydroblocks, manufacturers have developed automatic transmission repair kits. A complete set of parts is formed for each automatic transmission. The kit includes all commonly used parts: gaskets; seals; friction clutches; oil seals.

The makeup of an automatic transmission repair kit may vary depending on the manufacturer. Variety of kits: Master Kit; Overol; Banner.

Hydraulic-block automatic transmission – Signs of malfunction | Design | Principle of operation

Hydraulic Transmission Block

During operation, the hydroblock on automatic transmissions is subjected to considerable stress. Improper use or poor maintenance may cause the hydraulic unit to fail and require costly repairs. Depending on the gearbox design and engine location, the hydroblock is both easily accessible and not.

Contents :

  1. Principle of hydroblock operation
  2. Causes of breakdowns
  3. Self-repair

Hydroblock | Working Principle

Why does the hydroblock malfunction?

Failures of the automatic transmission hydroblock can occur as a result of improper operation of the transmission. For example, the car owner may not wait for the transmission fluid to warm up in winter and start driving in the most active mode. In some cases problems with cooling system are observed, which appear as a result of lack of coolant replacement and wrong functioning of oil intake. All this can lead to breakdown of the hydroblock and the gearbox itself.

Damage can be accompanied by a variety of hydroblock symptoms. It should be noted that despite the development of computerized vehicle diagnostics systems, it is difficult to accurately determine the breakdown of this element. Therefore, during service work, masters can determine the breakdown only by dismantling the box.

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Hydraulic cylinder assembly photo

The principle of operation of the hydraulic cylinder of the automatic transmission is quite simple. It transmits fluid pressure (ATF) through specific channels to the mechanical parts of the automatic transmission, it all depends on the necessary action, and on what gear is on. All this complex process is controlled by the ECU (Electronic Control Unit). It should be said that due to the increased loads this element is not reliable and has a higher percentage of breakdowns than the entire automatic transmission as a whole.

READ ALSO – WHAT DOES AN AUTOMATIC TRANSMISSION CONSIST OF? Transmission oil pump Friction packs Transmission converter Transmission electronic unit (ECU) Solenoid unit

Hydroblock malfunction LED


A typical symptom of an automatic transmission hydraulic unit malfunction is excessive vibration and grinding during gear shifting. In some cases a complete halt of the engine may occur while switching from the Park mode to Drive mode. Also quite often the malfunction is manifested by jerks, bumps and slips between gears. Modern cars, equipped with numerous sensors, in case of breakdowns display a message about the damage of the gearbox. It is only possible to determine the exact cause of the failure by connecting a computer to diagnostic equipment and conducting the appropriate gearbox tests. In this case, you will be able to identify the failed element. However, it is impossible to tell the exact nature of the failure even after computer diagnostics. It is necessary to dismantle the hydroblock and disassemble it.

Picture of automatic transmission hydraulic unit

A picture of an automatic hydraulic unit

Is self-repair possible?

The hydrogroup may be repaired in specialized workshops and service centers. Repair of the hydrogroup of an automatic transmission with your own hands is possible only if you have practical experience in working with similar spare parts. You will need to dismantle (in some cases) the automatic transmission, open the case and first of all check the valves. You most likely will not be able to clean them yourself, as it requires professional equipment. Also be sure to check the hydrogroup springs, which tend to wear out. Reassembly of hydrogroup design is very important, if you will make a mistake – consequences may be much more sad than replacement of only one part in an assembly. As you can notice, only an experienced specialist can perform repair work if he has the appropriate equipment.

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Hydraulic Block Diagram

hydraulic module diagram

The cost of hydrogroup repair directly depends on the nature of the breakdown. For example, problems with springs, valves, solenoid block are quite common. Many service stations do not undertake the repair, reasoning that it will be cheaper to replace it as a complete unit. This is not always the case, you can contact us and we will gladly perform repair of hydroblock inexpensively and qualitatively. Due to the fact that the structure of hydroblock is quite complex, consisting of a large number of parts – it is required to have a huge stock of knowledge and experience in order to perform such repairs. The cost of such repairs can range from 10,000 rubles, to several tens of thousands of rubles. There is also the problem of a clogged hydroblock, when the valve plate spools begin to stick. In some cases it makes sense to replace the broken element instead of trying to perform an expensive and complicated repair procedure.

Hydraulic Transmission Block Repair – Video

Of the preventive measures to prevent hydroblock breakdowns, we recommend that you closely monitor the condition of the transmission cooling system. The malfunctioning of the cooling system is one of the most common causes of damage to this element.

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A car owner should also properly operate his car and automatic transmission in particular. You should not start the car especially in winter season without preheating the oil in the gearbox. This procedure takes only a few minutes and makes it easy to bring the temperature of the oil in the gearbox and the hydroblock to the desired temperature. In this way you can ensure quality cooling and lubrication of moving elements.

To warm up the transmission, you need to put the selector in the Drive (D) position and hold the brake for one minute. Immediately after that you can start driving. You should also remember that after starting to drive a cold car it is not recommended to crank the engine more than 3000 rpm. By following these simple rules, you can protect the gearbox and hydroblock from damage and prolong the trouble-free life of your car.

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