Automatic Transmission Valve Body Functions and Failure Symptoms

January 3, 2017 | Transmission

In this post we will discuss about the main parts of automatic transmission called VALVE BODY. What is the main functions of valve body? What is the symptoms will occur if the valve body malfunction? You will find all the answer after you read full article below:

Basic Function of Valve Body

All automatic transmission systems have a valve body which serves as its main control center. Basically, there are numerous passages and channels within the valve body which direct the flow of hydraulic fluid to different valves in order to activate the right clutch and shift the gear appropriately based on the driving situation. The valves that make up the valve body each serve a different purpose and their names reflect what they do. For example, the valve body has a 2-3 shift valve which is responsible for up shifting from 2nd gear to 3rd gear. And if there’s going to be a downshift from the 3rd gear to the 2nd gear, then the 3-2 shift valve would be responsible for that.

Types of Valve Body

Commonly, there are two types of valve body, first type is electronic valve body which using electronic system ECT (electronic controlled transmission) as main control to operate all shifting on automatic transmission. And many newer cars using this electronically controlled transmissions (ECT) which have bands and clutches that are operated from hydraulics. However, an electric solenoid valve is used to control each hydraulic circuit. This is what allows the transmission to have more elaborate and advanced control schemes than the non-electronically controlled transmissions. The controller of the transmission can monitor the throttle position, vehicle speed, the anti-lock braking system, and the engine speed.

And  another type of valve body called hydraulic valve body, all system works using hydraulic pressure and controlled by each valve that linked to the shifting handle.  When you change the handle’s position, it will uncover and cover certain passages in the valve body to accommodate that position. So, if you were to change the gear handle to “Drive,” then fluid would be directed into the clutch and the 1st gear would be activated.

Failure Valve Body Symptoms

If you have a failing automatic transmission valve body, there are some clear symptoms that you should look out for. Many of the symptoms simply have to do with the noises that you hear when you change gears. If you were to hear banging noises when you slow down, change gears, or travel in reverse, that would be one indication of a faulty valve body. Another symptom would be if the gear shifting stick slips a lot when you try to change gears. If the valve body were working properly, this shift stick would not slip so easily like that. You may also notice that it is much slower for your transmission to go into reverse or drive when you change the gear. All these are signs of a failing valve body in your automatic transmission system.

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It is easy to ignore these kinds of problems in the beginning because they are not so intense. But the problems with your valve body will become very clear if you drive your car continuously for at least 30 minutes because your transmission will start to get hot. If you experience any of these problems, take your vehicle to the nearest auto body shop right away and have a professional look at your valve body to see if it needs replacing.

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