Technology has made great strides in making gear shifting effortless, This is mainly due to additions to the automatic gearbox itself. Components such as; synchronises, planetary gears and valve bodies, have made gear changing smooth. The automatic gearbox’s valve body controls transmission shifts and directs transmission fluid to assist in shifting, preventing automatic transmission failure.
In the following guide, you will find more about the automatic transmission valve body, its function and the signs of a bad valve body.
What is Valve Body in Automatic Transmission
The valve body is a fundamental element that helps in performing the correct operation of automatic gearboxes. It is also known as the ‘brain’ of the gearbox, it is the most complex and critical component of the automatic transmission.
Besides, follow this guide, if your car transmission is failing.
Valve Body Functions
The valve body works like a brain of the automatic gearbox. Controls transmission shifts and directs the proper fluids into the proper passages to aid in shifting. All this allows the transmission to work properly and prevents premature damage to the automatic transmission.
Valve body parts or components
- Hydraulic block (valves, springs, balls, filters, oil passages)
- Solenoids (electro-hydraulic actuators)
- Sensors: speed, pressure and temperature.
- Wiring or electrical board
In addition to these components, the valve box needs a control unit to manage it for its operation. The control unit is responsible for controlling the operation of the valve body. For this, it continuously sends and receives information from other control units, sensors or vehicle control units, such as the engine and ABS control units, to recognise real driving conditions.
Valve Body Location
The valve housing is usually located inside the automatic transmission case, at the bottom of it. It is usually visible when the gearbox housing is removed.
They are usually immersed in the gearbox oil and their size can vary depending on the size of the gearbox. Some are on the outside of the gearbox, but most are on the inside and the gearbox housing needs to be removed to replace the valve housing.
Signs of Bad Automatic Transmission Valve Body
The most common sign of a failing valve body is various types of gear changing problems. These shifting problems include incorrect shifting, improperly timed gear changes, or harsh gear changes. It could also cause transmission slippage.
When it comes to detecting faults in the valve body, many experts pointed out that it is not easy, since they are not initially intense. The symptoms begin to become more evident as the transmission heats up and the most common are:
Knocking Noises
These occur when the gear change is made. The appearance of knocking noises is a symptom of a bad valve body that occurs when the vehicle speed is reduced, driving in reverse or changing gears.
If when slowing down, putting the reverse gear or changing the gear you hear knocks. These types of noises also indicate that the valve body isn’t in good condition.
Slow When Changing Gear
If we notice our car slowing down when entering reverse gear or when driving we notice the gear changes slowly, it is another sign that something is wrong with our automatic transmission system.
Check the engine light on
If any of the above symptoms occur and the check engine warning light or malfunction indicator light illuminates, check to see if the vehicle has any car diagnostic code.
Since the transmission valve system is responsible for many transmission functions, various transmission-related trouble codes may appear. These are P0715, P0751, P0783, P0829 and P2707.
RPM Increases During the Shift
If the transmission is working properly, the engine revs should drop between each gear change (for example, from third to fourth) to reach the top gear.
Gear Lever Slips
If the lever slides more than necessary when changing gears, something is wrong with the valve body since this element ensures that this situation does not occur.
If a mechanic confirms the failure of the valve body, the possible solutions are to replace or rebuild the part. Rebuilding is the least expensive alternative and is ideal when many of your components are not damaged.
Besides, here are some common gearbox problems and their solutions.
Automatic Transmission Valve Body Types
There are two main types of valve bodies: electronic valve body and hydraulic valve body.
Electronic Valve Body
The first type is the electronic valve body, which uses the electronically controlled transmission (ECT) as the primary control to operate all gears of an automatic transmission. Many newer vehicles use ECT, in which the belts and clutches are hydraulically controlled.
However, a solenoid valve is used to control the various hydraulic circuits. This allows the gearbox to have more extensive and complex controls than gearboxes without electronic control. The gearbox control unit can control throttle position, vehicle speed, anti-lock brakes and engine speed.
Hydraulic Valve Body
Another type of valve body is called a hydraulic valve body. In this system, each valve connected to the gear lever is controlled by hydraulic pressure.
When the lever position is changed, specific ports in the valve body open and close according to this position. Therefore, when the shift lever is moved to the ‘Drive’ position, fluid is supplied to the clutch and the first gear is engaged.
These are some of the common signs of a bad valve body. As with most automatic transmission parts, these components don’t come cheap to replace, as the work often has to be done by a professional. If the fault allows it, it may be advisable to repair the existing valve block.
If the replacement cost is higher, then you can think about buying a used car for sale in the UAE and avoid extra repair expenses.
In any case, the best way to save money is to stop driving as soon as a fault is suspected and have it checked immediately to prevent further damage to other parts.
If this guide helps you identify the bad valve body symptoms, stay tuned to the UAE’s leading auto blog for further assistance.
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