Transmissions: How do they work? [Infographic]

What is a Car Transmission?

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Engine Speed Vs Engine Torque

The first step in understanding your car’s transmission is to grasp the difference between engine speed and engine torque. In simple terms, engine speed is the number of rotations the crankshaft makes in a minute (RPM). Engine torque, on the other hand, is the amount of twisting force created by the engine at any speed. Kind of complicated right? Perhaps an analogy might be easier to understand.

Like a Hammer and a Nail

To make these concepts easier to understand, think of a hammer and a nail. Speed is the number of times you hit the nail in one minute. Torque will then be how hard the nail is hit each time. If you speed up hammering the nail, chances are that you will miss the nail head more often because of the pace of your hand movement. At the same time, the force you put into the nail will be reduced because you have to reduce the distance between the nail and hammer to account for the increase in speed. By the time you actually get it all the way through the wall, your arms will be aching from the repetitive motion. But, if you try going very slow and precise, while you will be able to deliver a more forceful blow, it will still take longer to drive the nail through the wall. This is not efficient either.

Perfectly Balanced, As All Things Should Be

The most efficient method of driving the nail into the wall is to hit the nail with the right pace AND the right amount of force with each strike. This gets the job done without straining your muscles. Doing it just right is the key; not too fast and not too slow.

Keeping the Speed Just Right

Your car’s crankshaft has to move at the right speed, just like the hammer, to avoid damage to the engine. This is done by adjusting the amount of torque is applied depending on driving conditions. When your vehicle is at a standstill, it requires higher amounts of torque to get to speed, while at high speeds, your vehicle needs a lot less power to maintain speed due to Newton’s first law of motion. This law states that an object in motion tends to want to stay in motion and that an object at rest wants to stay at rest. That’s where the transmission comes in; your vehicle’s transmission is able to regulate the amount of torque is applied to increase or the power given to the wheels using a series of differently sized gears in its gearbox. The engine generates power and rotates the crankshaft. The transmission then adjusts torque to multiply or divide the power depending on required speed and conditions and then drive wheel then receives the adjusted power and increases or decreases speed.

Keeping The Ratios in Gear

The amount of torque is determined by gear ratios. Each gear has varying numbers of teeth depending on the size of the gear. These gears contact with each other and increase or decrease torque without affecting the engine’s rotational power. The input gear is effectively generating the power and the output gear is receiving the power. If the input gear has 20 teeth and the output gear has 10 teeth then the ratio is 0.5 to 1. The first gear is spinning slowly but causes the last gear to spin quickly. The gearbox contains many gears with different sizes and amounts of teeth and changes which gears are engaged with each other as the vehicle shifts. The higher the gear used, the lower the ratio of rotations required to turn the output gear. In 1st gear, the input gear must turn 3.1661 times to turn the output gear once. This proves that at high speeds you don’t need as much power, but starting from a standstill or going up hill requires higher torque and power.

Why is the Transmission so Important?

In summary, the transmission helps the engine not waste the power in generates. It makes sure that the power created is just right to turn the wheels. If the conditions need more power, it goes into lower gear ratios to allow more efficient usable power at low speed. If less energy is needed, power to the wheels is reduced and lets the crankshaft maintain the rotational speed.
All of this amounts to improving fuel efficiency and keeping your car’s engine healthy.

Think You Might Have Transmission Problems?

Having trouble shifting or hear odd noises coming from your vehicle? AAMCO Colorado can diagnose your problem with our exclusive Transmission Vehicle Courtesy Check service. Schedule an appointment today with your local AAMCO Colorado service center and we’ll get your transmission repaired, maintained or rebuilt right the first time.

We know that sometimes money can be tight, especially when it comes to proper vehicle maintenance, however, AAMCO Colorado is on your side. Our expert technicians will either let you know that your transmission is just fine or they will identify the problem before it turns into a much bigger one. Let us help you get back on the road safely!

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