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 (18)
My 2003 Corolla will refuse to move when I shift the gear stick to drive or reverse until I step on the throttle pedal then the car will move with a gerk, and while driving atimes it goes on neutral before changing to another gear, the dash board is showing the check light, what could be the problem pls.
My Transmission drop power and pinking up power
I need to buy a BMW X3 gearbox 6hp-26x
My kzte won’t engage reverse gear and when on drive it not go on up hilled ways it only moves on flat roads
I have a Toyota Camry model 2013 my mechanic said the valve body is bad ,we change more than five,yet the vehicle is still doing the same thing he now suggest l should replace the gearbox how possible it is
I had an automatic transmission when I tried to shift into manual and observe ever gear, found it will only stay in the 3rd gear, what is the root caused of the problem? My unit is Chevrolet trailblazer.
Also noticed it’s throttle body observed the flaps inside did not move, always stays in open position, what is the root caused? Is it already defective Throttle Body?
2015 kia optima automatic goes into drive nuteral and reverse but won’t move either in forward or reverse. What could be the problem please?
I have a 2015 ram 3500 with a 68rfe it was built for 700hp.
I’ve recent been having issues with it shuddering when shifting from 1-2-3-4 under full throttle(never used to) almost like the driveline is going to fall out. (Not the case everything is tight) if I’m half to 3/4 it doesn’t do that it shifts nice.
Now if I come up to a corner and let the truck just downshift on its own once I get around the corner and hit the pedal it’s almost as if it’s in neutral for a split second then it bangs into gear.(so I manually shift now and it doesn’t do it) it’s usually cause it’s coming down from 3rd to 2nd gear. So I’ll just manually put it to second so I don’t hurt it further.
Also when I start the truck warm or cold and try to put it in gear after a few seconds it barely moves(it should idle itself at 7-9km/h.
So after the novel I’m wonder if anybody has a good idea what that could be. Or if anyone had a similar issue and found a solution.
Thanks for reading
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
2AZ engine valve body problem