The Symptoms of a Failing Transmission Valve Body

The Symptoms of a Failing Transmission Valve Body

Next Gen Drivetrain Research & DevelopmentAugust 14, 202110 comments

The valve body is a major component of any transmission. It is a control center that looks like a maze filled with valves, passages, and solenoids that divert transmission fluid where it’s needed. The transmission valve body isn’t known to fail all that often, which is a good thing. But when it does fail, you are left with one of two options, both of which will be expensive – either rebuild or replace it. Get familiar with the symptoms of a failing transmission valve body so you can take some preventative measures.

How It Works

All automatic transmissions have a valve body that acts as the brain of the transmission. Within, there are dozens of passages and channels that direct the flow of hydraulic fluid to different parts of the transmission. This is in order to activate the right clutch pack or band and shift to the most appropriate gear based on the speed of the vehicle. Each valve has a different purpose and they are named to reflect that job. The valve body has a 1-2 shift valve that is responsible for shifting up from first to second gear.

Symptoms of a Failing Valve Body

Delayed Garage Shifts

One of the most common symptoms of a failing transmission valve body is a delay in shifting or harsh shifting. Usually called garage shifts, it’s when there is a harsh shift from park to drive or drive to reverse. Try to limit the number of times you are in that situation, even if it means backing into the garage.

Incorrect Shifting

When driving, you could notice the transmission shifting into higher or lower gears at the wrong time. You could be struggling to get up a large hill, and for no reason the Allison transmission can shift into a higher gear, making the climb even harder. Another example is driving on a flat highway at 65 mph and the transmission shifting into another gear for no reason at all.

Shift Flares

When a transmission is working properly, there should be a drop in the RPMs on an upshift to match the higher gear in between every shift. A shift flare is when the opposite happens; the RPMs will increase, and the engine will rev up in between gears.

Gear Slippage

Gear slippage doesn’t always mean a failing valve body. The culprit could sometimes be low transmission fluid or worn transmission bands. But, it could also mean the valve body is going bad. A slipping transmission means your truck is trying to upshift but then falls into a lower gear. It might even refuse to shift into higher gear, which makes the engine higher than necessary.

Comments (10)

Oliver Elder on November 24, 2023

I have a 04 envoy and it doesn’t down shift when coming to a stop and wants to pull off in 2nd or 3rd gear

Hebert Mwanachiwena on November 24, 2023

2AZ engine valve body problem

B Hausam on May 04, 2023

My 2004 F150 has been in the shop for 6 weeks must be and they said they got the valve body and put it in the truck and it still didn’t fix the problem and now they told me they’re gonna take the valve body out and try to fix the valve.body. the part is poste to be brand new. Shouldn’t they be taking the next step?

JOHN on February 08, 2023


samara on August 20, 2022

my 2013 ford fusion has a check engine light on and i went to auto zone and they said to replace my transmission valve body assembly but i’m having no problems whatsoever with any harsh shifting or anything. so i’m wondering if it’s a messed up sensor or what.

Stephen on May 06, 2022

My 2007 Explorer has a really harsh shift from Park to Reverse after a rebuild. All bands are good, so thinking it might be a VB. Hiw do I know if my VB is bad? No leaks showing, although after one particularly violent reverse shift it popped a radiator pipe off…! Any help would be gratefully received.

Gabriel Enearu on May 06, 2022

I used 10 pin gear box in my Toyota sienna 2004, is refused to move back when I put the gear in Rev,
And when driving it will not change for one to other gear,
What is the problem please

Vincent on March 15, 2022

Isuzu kb300 lx automatic gearbox problem with the valve body can you repair it

jessica on January 25, 2022

my 2003 chevy trailblazer is hard shifting sometimes not at all at first it was not and i replaced all solenoids except for the solenoidthat connects to the wiring harness and i put lucas and blue devil and changed the fluid and filter now it is shifting first to 2nd but no third gear and forth gear sometimes dont want to keep spending money and not solving the problem can someone please give me advice

Shammy Peterson on September 30, 2021

It caught my attention when you said that when you notice that the transmission shifting into higher or lower gears at the wrong time, your valve body must be failing. This makes me consider going online to shop for a replacement solenoid valve. Since Tuesday morning, my transmission’s solenoids have been failing and have been performing erratically. It is ímportant for me to ensure my safety while on the road, so I will do your tips.

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