In a Clutch

Welcome back! Time to find out exactly what the One Way Clutch is that I mentioned last post. But before that, like always, time for a quick recap & review some definitions.


Previously on Anthony’s Automotive Blog….


Last week, we dived a little deeper into what is exactly involved with the Torque Converter and why you have one in the first place. Want to do a quick re-read? You can find it here.  For the recap, keep reading.


The Torque Converter can be found mounted between the engine and the transmission. It is made up of 3 different parts: the pump, the turbine and the stator. And its whole purpose for being is to make sure your engine keeps running when it is shifting between gears, coming to a stop or is not moving at all, aka idling.


There is one word added to this week’s vocabulary list: Sprag. You can find its definition at the bottom of the list. We’ve added a lot of words to your automotive dictionary these past couple of weeks. So much so that I am now going to start narrowing it down to just specific terms that are in relation to the week’s topic only. 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.

Torque Converter – A device that transmits or multiplies torque generated by an engine.

Gear – One of a set of toothed wheels that work together to alter the relation between the speed of a driving mechanism (such as the engine of a vehicle or the crank of a bicycle) and the speed of the driven parts (the wheels).

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.

Planetary Gear System – A gear system that consists of one or more planet gears (the gears in the middle area) that rotate or revolve around a sun gear (the gear in the center) and a ring gear (the gear on the outer edge).

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.

Turbine – An engine or motor driven by the pressure of steam, water, air, etc. against the curved vanes of a wheel or set of wheels fastened to a driving shaft.

Stator – A fixed part forming the pivot or housing for a revolving part, as in a motor, dynamo, etc..

Sprag – A device for preventing a vehicle from rolling backward on a grade.




You Got Sprag….


A One Way Clutch is also known as a Sprag Clutch. The definition listed above is the one that is listed in the Webster’s Dictionary that I like to reference. There is another definition of Sprag that could be listed here. It is this:


            A simple brake on a vehicle, especially a stout stick or bar inserted between the spokes of a wheel to check its motion.


It is definitely a beefier definition than the one listed in the dictionary and it better describes the function of a One Way Clutch. It allows a part to move in one direction but not in the opposite direction.

An easier way to think of how a One Way Clutch works is to think of how a bicycle works. If you push the pedals in a forward motion, it moves the bike. But if you try to move it backwards, most bikes won’t. The pedals move freely but the wheels of the bike don’t. Most bikes do this. In fact, I remember many times as a kid when going downhill, we’d like to try to spin the pedals backwards fast and then stick our feet out while we coasted. Fun times!

Now let’s do that with your car. Start it up. Put your hand on the shifter and drop it into Drive. Push your foot on the gas pedal and start moving. You are technically in first gear and you are moving. Now, lift your foot off the gas. Does your car instantly stop moving? No! It’s kind of like you are coasting. Now put your foot back on the gas and you find yourself moving again. Take your foot off the gas again and yep – you are back to ‘coasting’. This is the One Way Clutch in action.

In First Gear while in Drive is where you will typically experience the One Way Clutch. The same thing happens when you have your car in Neutral, which is like you have ‘no gear’ engaged but the engine is still running. And speaking of Neutral….


gears of an automatic


Low Gear, First Gear, Neutral, Reverse – Just Drive!


How many gears are there exactly that you can choose to have an automatic transmission in OR exactly what is this alphabet soup on my shifter? Typically you will find what is in the picture above: P R N D 2 L  or   P R N D 2 1

P is for Park. This is when no gear has been selected and the gears have been locked to stop the vehicle from moving.

R is for Reverse. This is when the Reverse gear has been selected and will cause the vehicle to move backwards.

N is for Neutral. This is when no gear has been selected but the gears have NOT been locked and means the vehicle can and/or will move. You can push it and it will move. If you are on any kind of slope, it will roll all on its own. Neutral and Hills do not mix!

D is for Drive. This is your preferred choice, especially if you want to move. What Drive means is that all the gears are available for your car’s use when propelling the car forward. This means the progression from first gear to second gear to third gear to fourth gear and beyond will be done as you continue to accelerate.

2 is for Second Gear. This is when you limit the gear selection. In this setting, you have made only First and Second Gears available for your car to use.

L or 1 is for Low/First Gear. Just like the Second Gear setting except you have limited the gear selection to First Gear only.


You may see more letters or numbers than what is listed above. If it’s a number, then that typically refers to the highest gear that you are making available for your vehicle to use. If there are any specific letters that you’ve seen that you have a question on, comment or shoot us an email. We’d be happy to clear up any confusion for you.


Until Next Time….