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📘 How Car Transmissions Work

An engine wants one speed band; wheels need many. A transmission trades rotational speed for torque through selectable ratios.

5
lessons
~25 min
to learn
Adults
level
Start the course →

What you’ll learn

  1. The ratio problemExplain why a car needs changing speed-torque ratios and how the final drive and differential fit into the drivetrain.Transmissions trade rotational speed for torque so one engine can launch, climb, cruise, and reverse a car.
  2. Manual gearboxesDescribe the clutch, constant-mesh gears, and synchronizers in a manual transmission.A manual gearbox uses a clutch for separation, synchronized engagement for smooth shifts, and selected gear pairs for fixed ratios.
  3. Torque-converter automaticsTrace fluid coupling, lockup, planetary gearsets, and hydraulic clutch control in a conventional automatic.A torque converter smooths launch, planetary gears create ratios, and controlled clutches and brakes change the power path.
  4. CVTsExplain how pulley diameters, belt clamping, and continuous ratio control distinguish a CVT.A CVT changes effective pulley radii continuously so the engine can stay near a useful speed without fixed gear steps.
  5. Choosing the architectureCompare transmission architectures as different solutions to vehicle efficiency, performance, control, and packaging tradeoffs.Manuals, automatics, dual-clutch systems, CVTs, and hybrid power-split units use different hardware and software to manage the same engine-to-road problem.

Questions this course answers

Put the main drivetrain elements in power-flow order

The engine supplies rotation, the transmission selects a relationship, the differential distributes it, and the tires turn torque into road force.

Why does a low gear help a car launch?

A low ratio trades output speed for greater output torque, which helps overcome inertia and road load.

Why does a manual car need a clutch pedal?

The clutch allows speed matching and controlled re-engagement instead of forcing mismatched rotating parts together.

Match each manual-transmission part to its job

These parts divide the work of disconnecting, matching, and transmitting the selected ratio.

What lets an automatic transmission hold the car stopped in Drive without stalling the engine?

The converter can transmit rotation hydraulically with slip at low vehicle speed, allowing the engine to keep running.

Put a planetary-automatic shift sequence in order

Sensors inform the controller, pressure is routed, the gearset roles change, and the new ratio carries the load.

Grounded in trusted sources

  • Toyota, Types of Transmissions, https://www.toyota.com/car-tips/types-of-transmissions/
  • HowStuffWorks, How Automatic Transmissions Work, https://auto.howstuffworks.com/automatic-transmission.htm
  • HowStuffWorks, How CVTs Work, https://auto.howstuffworks.com/cvt2.htm
  • Cars.com, Automatic Transmission: What You Need to Know, https://www.cars.com/auto-repair/glossary/automatic-transmission/
  • Cars.com, What's a CVT?, https://www.cars.com/articles/whats-a-cvt-418856/

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