Transmission Valve Bodies: Rebuild or Replace?

One of the most important components of the transmission is the valve body. Its importance is such that mechanics call it “the control center of the transmission”. For that reason, when there is a problem with the transmission valve body, it is logical to wonder if it is more convenient to rebuild it than to replace it.

Below, on the Sun Transmission blog, we'll tell you everything you need to know about the transmission valve body so you can make the best decision for you.

What is a Transmission valve body?

The valve body is a vitally important component in any automatic transmission. It is usually made of aluminum and its function is, basically, to send the transmission fluid at the right time to the different valves and channels that compose it, to control and manipulate the gear shift. Simply put, it is the conductor of the orchestra within the transmission.

How does a Transmission Valve Body Work?

The way a valve body works is in accordance with the requirements of the gear, i.e., the valves that compose it open and close to send the transmission fluid (ATF) to where it is required for the gear changes to be correctly coupled. This operation is executed by body circuits, which are controlled by a system of valves and solenoids.

It is a matter of the position of the solenoid to activate a different circuit specific to the transmission.

Valve Body Components

Although the operation of this system may seem simple and basic, the structure and elements that integrate it are more complex, let's see which are the main ones:

• Hydraulic block. It is the main piece, in it we will find all the valves, channels, solenoids and more components of the valve body.
• Valves. These oversee controlling the flow of hydraulic fluid. We find change, pressure and acceleration valves. They open and close to direct the fluid to where it is required.
• Solenoids. These are the ones that receive the signal emitted by the Electronic Control Unit (ECU), to generate a magnetic field, which will open and close specific valves to control the fluid flow.
• Channels. The fluid flows through these ducts. Their design is key to guarantee correct and efficient flow where required.
• Springs. These are used to ensure a tight seal on the valves when required.
• Sensors. In charge of reading elements such as pressure, temperature and speed of the car to provide information to the ECU so that it can make correct decisions about gear changes.
• Check balls. Practically, they act as a barrier to prevent a fluid from going in one direction only and not in a reverse direction.

Which Valves Work in the Valve Body?

In this component there are three main valves, which together complement the correct operation of the valve body.

• Valves that regulate the hydraulic fluid pressure inside the transmission, these are the ones that open and close according to the signals received from the system.
• Valves for gear change, as its name indicates, are responsible for making the required changes in time and form. They direct the liquid to the clutch and transmission belts to perform the gear changes.
• Directional control valves, in charge of controlling the direction of the transmission fluid.

Valve Body Types

We found two main types, this mainly because of the expansion of the use of electronic systems in cars from the beginning of the century onwards, but previously, there was no such technology. Let's see a little more of this.

Hydraulic valve body

This is a totally mechanical component, in it we find the butterfly valve that works by means of hydraulic pressure and in this way, controls the movement of the shift valve.

Electronic valve body

The one we find in all vehicles nowadays. This type of system is more precise and friendlier with gear changes. Its operation is composed of an electronic system, solenoids, sensors and is related to the vehicle's ECU.

Common Problems with Valve Bodies

Like any other component of a vehicle, the valve body can present several problems, some more serious than others, but all of them need immediate attention if we do not want to aggravate them. Let's look at the most common ones.

• Fluid contamination: if the transmission fluid is dirty, for example, with metallic particles derived from wear, it can clog channels and valves, which will affect fluid flow.
• Fluid lost properties: over time, transmission fluid will lose its lubrication benefits, its consistency may become viscous, and this will impact valve operation.
• Component wear: from sensors, solenoids to the valves themselves. Thisything that makes up this system can suffer wear and tear, which will undoubtedly be reflected in its operation.
• Clogged channels: this derives from the formation of fluid residue deposits, which can begin to accumulate, generating internal restrictions that will prevent correct flow.
• Electronic problems: directly related to sensor failures, which due to wear and tear or faulty manufacturing may emit incorrect signals.
• On the other hand, they can present failures in its programming or physical problems, which will result in a malfunction of the valve body and many other components of the vehicle.
• Damaged valve body: it is the whole component which may be damaged, either by a blow, or from the manufacture itself.
• Valve body gasket with wear: this gasket is responsible for sealing the body and prevent the transmission fluid from leaking, if this gasket is damaged it is possible that there is a low fluid level, which translates into problems for the automatic transmission in general.

Symptoms of Valve Body Failure

We have already discussed the common problems that occur in this automotive component. Now let's look at the main related failures.

• Abrupt or untimely shifts. This would be one of the main signs that something is wrong with our vehicle's transmission.
• Stalled gears. Another symptom will be that the vehicle circulates in the same gear, and it is not possible to change.
• Badly synchronized gears. By this we mean when the transmission shifts up or down at the wrong time.
• Slipping or “skidding.” When the vehicle has a hard time, shifting up a gear, increasing the RPM more than normal until it does.
• Atypical noises. The most common are knocking noises coming from the gearbox, as well as buzzing or grinding noises.
• Check engine light. On the dashboard of your vehicle this light came on, which indicates that a problem was detected, it may be related to the valve body or something else, it is best to submit it to a review with a scanner.

Rebuilding vs. Replacement

If cost is an issue, you may want to rebuild it. Of course, your ability to do so depends largely on the miles already logged by the transmission; the higher the mileage, the less feasible it is to rebuild it. The alternative, replacing it, is a bit more expensive, but sometimes necessary. If the rebuild option is not available, you may have no choice but to replace it.

How Much does it Cost to Repair or Replace the Valve Body?

One of the major components of an automatic transmission is the valve body. The cost to replace the transmission valve body can range from $390 to $860, with parts ranging from $250 to $500. In addition, depending on whether a dealer or an independent shop performs the task, labor alone can cost between $140 and $360 per hour.

Advantages and Limitations of Rebuilding

If you are on a limited budget, valve body rebuilding may be the best alternative. Since this component has many disposable parts such as gaskets, clutches and seals, they can be easily replaced to save money and repair a relatively simple problem.

However, it is essential to have a professional completely disassemble and inspect the transmission to ensure that all components meet the manufacturer's specifications.

Benefits and Considerations of Replacement

It is important to consider that a damaged valve body may indicate that there is more damage inside the transmission. For this reason, some mechanics opt for a complete replacement to ensure proper operation.

Whichever route you choose, you should always look to get the best parts available, like the ones you'll find here. At Sun Transmissions online store, you will find a wide variety of transmission parts online that you can buy and receive at home, such as power steering rebuild kits, automatic transmission cooler, automatic transmission additives, modulator valve transmission, transmission overhaul kit and everything for your rebuild needs.

We invite you to browse our blog and find all kinds of useful information related to the proper functioning of your vehicle, automatic transmission, electronic power steering and much more. contact us today!