One Valve, Two Valve, Three Valve, Four….

Welcome back! This week we are going to see what exactly the Valve Body is and the purpose it plays in your automatic transmission. But before we get into that, like always, time for a quick recap & review some definitions.

Previously on Anthony’s Automotive Blog….

Last week, we drilled a well and learned all about Texas Tea and just how important Oil is to your car’s transmission. You can do a re-read of it here. Or, keep reading for the quick recap.

Oil and the pump it goes through creates the pressure necessary for your transmission to function…period. It is this pressure that keeps the transmission fluid flowing throughout your car’s system, which, in turn, keeps it cool, changes gears and lubricates just about everything else and keeps parts moving. Let’s face it – we like moving parts.

We’ve added a few words this week: Pipe, Valve, Servo, Servomechanism, Servomotor, Solenoid, and Throttle. You can find them at the bottom of the list. As always, you can find our entire and current automotive dictionary here. Feel free to save its link so that you can find it again in case we use a word that happens to not be on this week’s list.

Our Growing Automotive Vocabulary

Here are the related words for this week’s topic. Enjoy expanding your vocabulary.

Transmission – The mechanism by which power is transmitted from an engine to the wheels of a motor vehicle.

Automatic – A device or process that works by itself with little or no direct human control.

Automatic Transmission – An automotive transmission that can automatically change gears as the vehicle moves, freeing the driver from having to shift gears manually.

Clutch – A mechanism for connecting and disconnecting a vehicle engine from its transmission system.

Band – Something that binds, ties together, restrains, etc.; a strip or ring of wood, metal, rubber, etc. fastened around something to bind or tie it together.

Pump – Any of the various machines that force a liquid or gas into or through, or draw it out of, something, as by suction or pressure.

Hydraulic – Operated by the movement and force of liquid; specifically, operated by the pressure created when a liquid is forced through an aperture, tube, etc..

Oil – Any of various kinds of greasy, combustible substances obtained from animal, vegetable, and mineral sources; oils are liquid at ordinary temperatures and soluble in certain organic solvents, as ether, but not in water.

Pipe – A long tube of clay, concrete, metal, wood, etc., for conveying water, gas, oil, etc. or for use in construction. Also, anything tubular in form.

Valve – Any device in a pipe or tube that permits a flow in one direction only, or regulates the flow of whatever is in the pipe, by means of a flap, lid, plug, etc. acting to open or block passage.

Servo – This is short for Servomechanism OR Servomotor.

Servomechanism – An automatic control system in which the output is constantly or intermittently compared with the input through feedback so that the error or difference between the two quantities can be used to bring about the desired amount of control.

Servomotor – A device, as an electric motor, hydraulic piston, etc., that is controlled by an amplified signal from a command device of low power, as in a servomechanism.

Solenoid – A coil of wire, usually wound in the form of a helix, that acts like a bar magnet when carrying a current: used in brakes, switches, relays, etc..

Throttle – The valve that regulates the amount of fuel vapor entering an internal-combustion engine or controls the flow of steam in a steam line. This is also known as the Throttle Valve.

Come in Houston! Do you read me??

Last week we talked about how the transmission fluid is the ‘blood’ that flows through your car. And, that it is the oil that creates the ‘blood pressure’ of the system. Using this same type of analogy, the Valve Body is the ‘brain’ of your vehicle. This is where everything is controlled. We touched briefly on the Valve Body and its purpose a while ago here.


A Valve Body

A Valve Body


In a nutshell, the whole purpose of the Valve Body is to smoothly shift gears as you are driving down the road. That is all. The Valve Body is an intricate & specialized maze of channels that directs the transmission fluid that activate whatever gears are needed to shift to.

For example, if the car needs to shift from second to third gear, the transmission fluid needs to flow through the channels to the specific valve that is for that function. This valve is often called the 2-3 valve. And oddly enough, there is a specific valve for shifting from third back to second and it’s commonly called the 3-2 valve. In this system, there is a valve for everything!


Simple Gear Shift Stick

Simple Gear Shift Stick


The most important valve is the Manual Valve. THIS is the valve that you actually have direct control over and basically gets the whole process going. The Manual Valve is the one that is directly connected to your gear shift. In an automatic transmission, the second you move the gear shift into the Drive position, the Manual Valve directs the transmission fluid to the clutch packs that activate 1st Gear. At the same time, it engages the monitoring of your vehicle’s speed and throttle position to best determine the correct time and force needed to do the shift from 1st Gear into 2nd Gear.

Most automatic transmissions nowadays are computer controlled with electrical solenoids mounted in the Valve Body to help with the direction of fluid to the appropriate clutch packs, bands or servos. This is done to make your car more efficient and to be more precise in determining shift points while you are moving.

My Sole….what??

It’s a Solenoid Pack. To further simplify the definition we listed above – It is simply a coiled wire that acts like a magnet when an electrical current is running through it. By acting like a magnet, it can easily open and close valves.

Now, in a computer controlled transmission, there are sensors that are used to capture lots of data related to your engine: brake pedal position, engine load (how ‘hard’ its working), engine speed, vehicle speed and many more. By compiling all of this information, it can exactly pinpoint when a gear shift needs to occur. AND when it has properly identified that moment, it transmits to the Solenoid Packs in the transmission so that they can redirect the transmission fluid as needed to the correct clutch pack/band/servo to shift the gear.

For Next Week

This week we’ve touched on how a computer controlled transmission works by interacting with sensors and solenoid packs. Next week, let’s go old school and take a look at how non-computerized transmissions work and what parts they have that differ from the computerized ones.

Until Next Time….

 Anthony’s Automotive


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