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Automatic Transmission Valve Body Functions and Failure Symptoms

When using a car, someone may have ignored some symptoms that they think are not serious. But in fact, these signals that your car gave you could be critical and needed you to act as quickly as possible. The transmission valve body symptoms are not an exception. In this post, we will discover what is a transmission valve body, automatic transmission valve body and the symptoms of bad valve body. Therefore, you can recognize the transmission valve body problems and fix it immediately to maintain the best condition of your vehicle.

What Is A Transmission Valve Body?

First of all, let’s find out what a transmission valve body is.

transmission valve body symptoms
Automatic transmission valve body functions and failure symptoms. (Source: Gilbert Arciniega @ Youtube)

The valve body is the control center of the automatic transmission.  It includes a maze of channels and passages that guide hydraulic fluid to the various valves which then activate the appropriate clutch pack or band servo for each driving situation to switch smoothly to the appropriate gear. Like a hydraulic fluid hose, each of those channels performs, somehow, the same job. It was much easier to mill out passages in a metal block instead of making a hundred horses running all over the place, thus keeping everything tidy as well as more reliable. Each of the many valves has a particular role in the valve body and has a name for that feature. The most important part of the valve body is the manual valve. Connected to the gear stick handle, it instructs the right passage for hydraulic fluid to pass through.

Recently, the modern automatic transmission valve body has sensors to monitor the speed, brake pedal position, throttle position and engine load to perform a soft and firm gear shift. The sensors send vital information to the onboard engine management computer. It further directs the electrically controlled solenoid that redirects the hydraulic fluid to the right clutch pack. Therefore, it will ensure a soft and seamless change between gears.

Now that you know about auto transmission valve body, it is time to know transmission valve body symptoms.

Failure Symptoms Of Automatic Transmission Valve Body

Although modern automatic gearboxes are strong and enduring, the overall reliability takes effect from the added complex structure to these systems. Therefore, the sooner we notice the abnormal signals of the engine, the longer we can maintain the use of it.

There are a few transmission valve body symptoms that keep you aware of failure activity of the engine. Most of them are quite noticeable. It is recommended that you should fix these problems as soon as possible. Then, your driving ability will be protected and gear changing will be smooth as usual. Here are the automatic transmission valve body symptoms that you must not ignore

1. Knocking Noise

One symptom of a bad valve body is strange knocking noises. You will notice the clunking or knocking noise coming from the gearbox when you brake, change the gears or when you accelerate. Chances are that you may hear some awkward noises when putting the car in reverse and driving backward.

The reason for this can be anything from inappropriate oil pressure to actual physical damage to the transmission valve body. Anyways, as soon as you hear strange sounds from the gearbox you should get your car a check.

transmission valve body
One symptom of a bad valve body is strange knocking noises. (Source: Firestone Complete Auto Care Blog)

2. Gears In Troublesome

Late gear shifts or general issues with gear changes are common transmission valve body symptoms. When the gearbox prepares to change gears, it will drop the RPM slightly. A bad transmission valve body probably makes the RPM spike for a moment. Whenever you experience these problems, contact your mechanic for a check immediately.

auto transmission valve bod
Late gear shifts or general issues with gear changes. (Source: ICsense)

3. Difficulty In Downshift

Similar to shift gears, you might have difficulty downshifting as one of the symptoms of bad valve body. This explains that hydraulic fluid is unable to enter the transmission valve body properly. Once this starts happening, the gears will not function properly, thus degrading the performance of the vehicle.

4. Delay In Shifting

Are you facing problems while changing your gears to reverse or drive? If you have ever had a long pause between going in reverse and being able to slide into drive, then you understand the pain of a delayed shift. Most often, it is because of the transmission valve body that is working improperly. Thus, the shifting of the transmission experiences a great delay. Be ready! Due to this, it may cause the car to be stuck in neutral.



When it comes to replacing a transmission valve body, cost is something to take into account, as it will depend on the labor and model of your vehicle.

An average transmission valve body will cost between $200 to $500. In addition, the labor costs tend to be quite intense as the process of replacing can take around 2 to 4 hours to finish. So, it is important to note that the hourly rate of a mechanic costs between $60 to $100. So you will pay between $120 and $400 for labor costs before taxes and fees. Therefore, the total cost of the valve body replacement will vary between $320 and $900.

Replacing a transmission valve body (Source: ManualesDeTodo.Net)

If there are transmission valve body symptoms that are serious, you will need to take into consideration if you need to replace the whole valve body or to fix the transmission system.

Tips For A Long-Lasting Valve Body

Because the cost for either replacing or fixing the transmission valve body is relatively high. It is better that you take care of the vehicle on a daily basis and keep track of the car’s condition.

The top advice to prevent transmission valve body symptoms is proper maintenance. Frequent maintenance appointments will let you know if there is any strange condition of your vehicle to fix it quickly and prevent further damages.

Also, you should use good transmission oil. Because using low-quality oils will lead to sub-par lubrication and cooling of the whole body. Later, that will make the key components’ lifespan shorter. In terms of economics, it will be cheaper if you use good oil than to rebuild the gearbox.

Last but not least, the easiest way is to always check the warning lights on your vehicle’s dashboard. Nowadays, cars are equipped with smart and clear dashboard for you to be noticed of any abnormal behavior inside it. But in case you do not have them, frequent maintenance check is always the best option to prevent transmission valve body symptoms or further damages of your car.

valve body transmission symptoms
Always check the warning lights on your vehicle’s dashboard (Source: Та4ани)

Sum Up

As mentioned above, the detection of a bad transmission valve body is relatively easy even with or without the help of an engine management computer. The best tip is to never ignore any unusual signs of your vehicle. Just like a human body, when you get infected by a virus, your body will get a fever, a cough or a running nose. Your car is the same. Try to look after your car as yourself and you can keep your vehicle always in green and strong.

Keep up with your pages for more useful information and tips that will help you know your car better.

  1. Taakoa. Bangke says

    So good to know all your technics and i can say thank you for sharing that…

  2. Lawrence kamau says

    My car is knocking while engaging gear no 3,what can be the problem?

  3. Vusa says

    my car had the knco sound i wud hear it more when i park and switch off the car. yesterday it was shaking terribly as if it wanted to change gears coz it had been travelling a while on first gear Nissan Tiida CVT and then struggled going uphill and when i eventually got her moving she stopped on the next inclined plane. now the car revs and all i put it on DRIVE smae thing reving but not moving . reverse same thing …

    as its reving but not moving … diagnosis had shown earlier that we need to change stepper motor and tcm sensor

  4. George Edward Burke says

    Hi Tsukasa,

    Thanks for sharing valuable information. Could you please suggest any good books to refer for automatic transmission valve body design.


  5. Ikaneng Thebe says

    which censor that needs to be replaced help pls

  6. shegzy says

    i have a mazda mpv 2003, the gear had been jerking at 2RPM since purchase as a used imported vehicle, but it started showing O/D off light flashing some days ago , and the transmission is behaving funny, experiencing slowdown at 2& 3 RPM along the jerking which is more pronounced now , even after changing the fluid. Codes PO328 and POO31 HO2S, but a car electrician inspected it thoroughly and said one fuse in the valve body of the transaxle is bad saying its better to get a new transaxle.What do u advise?

  7. Emmanuel Onyia says

    I have a 2015 Honda Accord which I just purchased from an auction. The car does move forward when the gear is put on ‘D’ or ‘S’, but would not go backwards when the gear is put on ‘R’ for reverse. What is the likely problem? How can the gear Reverse problem be fixed without changing the entire automatic transmission. Will changing the ‘Valve Body’ of the transmission solve the problem?

  8. Gregory says

    Nissan notr 2009 dont change from 1st into other gears pls help

  9. Thys says

    hi I have 2001 Toyota camry it has no kickdown and puls of in second gear please help

  10. Michael S Miller says

    Per technicians, I just had to replace the Automatic Transmission Valve Body in a 2016 Nissan Maxima (30,000 miles – under warranty). There was occasional slippage during gear shifting. The real concern is replacing the Automatic Transmission Valve Body in my 2018 GMC Canyon (500 miles). Vehicle failed to start, then started and seemed to run only in first gear. Purchased 3 weeks ago, 500 miles total, and in the shop still since DEC 8. Very concerning!

  11. Miguel Durand Ruiz says

    Hi p1716, p1754, p0748, U1000 these are my codes. My 350z Nissan 2004 from 10/03 automatic transmission. The TCM is a 2nd generation or type 2 TCM it is hard shifting from 2nd to 3rd gear.

  12. Wesley says

    Hey, I have a 1998 Galant automatic! Just as I start driving in D, the car revs. However if I start driving in the lowest gear it does not. Also while in the lower gear, it take forever to feel the car change over, what i have to do is change the gear from 1to2 to3 toD… this doesnt happen onces the car gets hot. It changes fine after… any ideas to whatvis wring?

  13. Steven Erwin says

    I have 2006 lexus gs300 RWD, I live in a hot weather place most of the year.
    My problem is when the car is still cold (didn’t reach operating temp.) I notice a delay of shifting in first and second gears but once it reaches the operating temp. everything is fine!

    what do you think could be the issue?!

  14. Eric says

    I notice a delay of shifting in third and fourth gears. Toyata Carmry 2011. everything is fine!

  15. Adetola says

    I have a 2008 Nissan Altima 2.5S, I noticed it jerks when I shifts from park to drive or reverse, I checked the transmission fluid and it’s alright.
    A week later , I wanted to drive out and discovered the car could hardly move when in drive and reverse, the movement was very slow and this made it undrivable so I had to leave it.i did a diagnostic with my obd tool and I got this two codes P0840 and P0845
    Please what could be the problem?
    Thank you .

  16. […] Valve body takes high pressured transmission fluid to determine which valve to open that decides gear ratio. The key is the pressure of the transmission fluid. Often called the brain of the transmission that contains passages to direct hydraulic fluid to valves. Its operation takes only milliseconds. […]

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