Drivers using automatic transmissions enjoy a lot of convenience on the road. Still, few are fully aware of the mechanisms that allow a car to change gears independently. One of the most critical transmission parts for this process is the valve body.
A valve body is a maze-like part of the transmission with plenty of passages and channels. The valve body and its solenoids push transmission fluid to flow through those passages to trigger different clutch packages and switch gears automatically.
So, if you’re wondering what a valve body is, this is the guide for you. Keep reading to learn everything there is to know!
What Is a Valve Body and How Does It Work?
The first question you’re likely to have is, what is a valve body in an automatic transmission? The answer is pretty straightforward: The valve body is the part that changes the gears.
A valve body looks like a maze built into a metal frame attached to the transmission. That maze consists of passages and channels through which transmission fluid flows.
When fluid flows a certain way, it’ll switch the transmission to the correct gear. That happens because the fluid activates the right clutch pack or band servo to suit your driving condition.
But what controls the flow of that transmission fluid? Well, that’s where the valve body solenoid comes into play. The solenoid is an electrically-controlled component that’s triggered to redirect the transmission fluid in a specific way to put your car into a particular gear.
Of course, all these functions happen automatically with little or no input from you. Modern cars come with many sensors that help the transmission decide which gear is necessary. Then, electrical signals are sent to the solenoid to redirect transmission fluid through the valve body as needed.
What Happens When the Valve Body Goes Bad? (4 Signs)
Unfortunately, there are no dedicated warning lights on the dashboard to tell you when the valve body is experiencing problems. Thankfully, valve body problems create several symptoms that let you know it needs help.
Here are 4 tell-tale signs that your valve body is going bad:
#1 Knocking Noises
The first sign of a valve body issue is a clunking or knocking noise coming from the transmission when you accelerate, slow down, or change gears. Worse yet, you’re bound to hear some painful noises when you try to put the car in reverse.
Knocking noises are pretty standard, coming from different car parts. So, don’t worry if that’s not enough. There are 3 other signs you can look out for.
#2 RPM Spikes When Shifting Gears
Another sign of a valve body problem is that your car’s RPM spikes upwards when shifting gears. That’s not normal because your RPM should drop when gears are changed.
This symptom is much more an indication of a problem with the transmission. Still, you'll need to inspect it closer to see if it's the valve body or another part that's causing the problem.
#3 Downshifting Problems
Remember: a valve body works by letting transmission fluid flow through different channels and pathways. However, if that doesn’t happen smoothly, you’ll start to notice your car having problems downshifting.
#4 Delayed Shifting
Finally, another clear-cut sign of a problem with the valve body is delayed shifting. Even though the transmission is meant to work automatically, you’re still likely familiar with when and how it normally shifts gears.
So, when you notice that shifting takes longer than what you’re used to, it’s probably a good time to troubleshoot your transmission.
What Causes Valve Body Failure?
Now we know what signs indicate a valve body problem, but what causes a valve body to go bad in the first place?
Reasons Why a Valve Body Goes Bad
There are three likely reasons, and these are:
- Contaminated transmission fluid: You've likely heard from your mechanic or other online articles that contaminated transmission fluid is bad news. Your valve body is a perfect example as to why that's true. Contamination affects the viscosity (its thickness, basically), which prevents it from working correctly.
- Not enough lubrication: The valve body has plenty of moving metal parts. Without enough lubrication, those parts end up rubbing against each other, causing the valve body to damage itself from the inside.
- Excess wear: Like any other car part, the valve body has a limited lifespan. After many years of service, the valve body and components will stop working correctly.
Can You Drive with A Bad Valve Body?
Yes, your car is still mobile even with a bad valve body, but you probably shouldn't be driving it unnecessarily. A faulty valve body means that your car won't be able to smoothly shift gears if it does at all.
That can put you in a precarious position, like needing extra power to go up slopes safely.
The only time you should ever drive with a faulty valve body is to get your car to a workshop to have the valve body fixed or replaced.
Can a Valve Body Be Repaired?
Yes, you can repair and rebuild a valve body that isn’t working correctly. That’s certainly a cheaper option than a complete valve body replacement.
Of course, that depends on how worn-out or damaged your valve body is. Like any other component, it’s possible to have a valve body that’s too far gone to repair. If that’s the case for you, a replacement is the only option left.
That might sound painful for your wallet at first. But don’t forget, you can shop at a Marketplace like the one at CarPart AU for second-hand valve replacements. Buying a used part will be cheaper, and it’ll still have plenty of value to offer.
How Much Does It Cost to Replace a Valve Body?
The valve body replacement cost is relatively high compared to many other spare parts, and there’s no getting around that. You can expect to pay anywhere from $400 or $500 to $1,500 or more for a brand-new valve body.
Of course, the final price depends on your car’s make and model. To give you an example, a new Volkswagen valve body costs around $5,000. Of course, not all brands will charge this high, but it’s worth knowing that the price goes that high for some cars.
Now that you’ve learned what a valve body is in a car, check out the Blog at CarPart AU for more informative articles. You may want to read next about what is a gear pump or what is an air flow metre. Learn something new every day!
By Ray Hasbollah