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  • Writer's pictureRobert Routt


Rebuilt Transmissions – Remanufactured Transmissions – Remans

Those of you who drive stick-shift cars may have several questions on their minds.

Is there any connection between the funny "H" pattern that I'm moving the shift knob through and the gears inside the transmission? When I shift, what happens inside the transmission?

What is actually grinding when I make a mistake and hear that awful grinding sound? As I speed down the freeway, what will happen if I accidentally shift into reverse? Is it possible for the entire transmission to explode?

This article explores the interior of a manual transmission to answer these questions and more.

Gasoline engines require transmissions because of their physics.The redline of any engine refers to the maximum rpm beyond which it cannot operate without exploding.If you read How Horsepower Works, you know that horsepower and torque are maximum at a narrow range of rpm.In an engine, for example, 5,500 rpm might be the maximum speed at which it produces its maximum power.When the car speeds up or slows down, the transmission changes the gear ratio between the engine and the drive wheels.The engine should be kept below the redline and near its best rpm range by shifting gears.

Manual Transmission
CVT Transmission vs Automatic

The transmission should have such flexible ratios that the engine can run at its single, best-performance rpm value at all times.Continually variable transmissions (CVTs) work on that principle.

CVTs offer a nearly infinite range of gear ratios.In the past, CVTs weren't competitive with four-speed and five-speed transmissions in terms of cost, size, and reliability, so they weren't used in production vehicles.Improved design has made CVTs more common these days.

Transmissions are connected to engines through clutches.Thus, the input shaft of the transmission turns at the same speed as the engine, resulting in improved power output and fuel economy.As automakers competed to achieve the best possible fuel economy ratings, CVTs became increasingly popular in hybrid cars because they are significantly more efficient than both manual and traditional automatic transmissions.CVTs were installed in one out of four American cars sold as of late 2016.

Since it is engineered for efficiency rather than fun, the CVT can be sluggish to drive. In spite of this, as fewer manuals are available due to drivers moving away from manual transmissions, CVTs continue to gain popularity. As a result, most trucks and large SUVs still use traditional automatic transmissions even in small cars with small engines.


Learn more about how continuously variable transmissions work by reading How CVTs Work.

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