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Automatic Transmission Valve Body Functions and Failure Symptoms

As the name suggests, automatic transmission valve body is a major component of a vehicle’s automatic transmission system. It works in a network form. The body directs pressurized transmission fluid to a network of valves that put together appropriate clutch packs for smooth gear functioning. Further, the valves use the pressure of hydraulic signals, determining the gear set, also known as servo. This process performs when the gear changes the speed from low to high or vice-versa.

Key Functions of Valve Body

Transmission valve body problems
Working of transmission valve body

An automatic transmission system has a valve body, which serves as the main control center. The valve body has numerous passages and channels within the valve body. It allows the flow of hydraulic fluid to different valves to direct the right clutch and switch the gear appropriately according to the driving situation. 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.

Now, 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.

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Failure Symptoms of Automatic Transmission Valve Body

Bad transmission valve body
Few transmission valve body symptoms

There are a few transmission valve body symptoms suggesting a bad transmission valve body. Most of these are quite noticeable. Chances are that one cannot bear these for too long as it affects the driving ability and causes frustration when changing gears. Here are the top symptoms that must not ignore.

1. Knocking Noises

When applying pressure to the brakes or slowing down the care, you might hear some banging or knocking noises. Chances are that you may hear some awkward noises when putting the car on reverse and driving backward. If your answer is yes to any of such scenario concludes that you have a bad valve body.

2. Slippage While Gear Shifting

If the shifting stick slips regularly when changing the gears, then there is likely a problem with the transmission valve body. Your shifting stick should never slip if the transmission valve body functions properly. That means there is something wrong.

3. Difficulty in Downshift

In case transmission is having difficulty in downshifting, it states that hydraulic fluid is unable to enter the transmission value 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 problem while changing your gears to reverse or drive? 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 stuck in neutral.

With the advanced technology, malfunctioning transmission detection takes place easily with the help of an engine management computer. It alerts the driver by activating a warning light on the vehicle’s dashboard. As one of the maintenance tips, one could do a timely inspection of the transmission valve body to enhance its functioning.

16 Comments
  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.

    Thanks!

  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

    Hi
    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?!
    Thanks

  14. Eric says

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

  15. Adetola says

    Hi,
    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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