How Torque Converters Work" How Transmission Coolers Work" When you carry small objects, like a book or a bag of groceries, you probably don't notice too much strain.
It's easy to carry small things around without breaking a sweat; you might even be able to toss them from one hand to the other. But when the weight of the object increases, the act of carrying becomes more difficult. Carrying a couch or a television, for example, is much harder than carrying a book. Your body will need to work harder and expend more energy to carry the extra weight, and chances are you'll sweat a little in the process.
The same principles apply to our cars. How Gear Ratios Work" If you want to create a high gear ratio, nothing beats the worm gear.
In a worm gear, a threaded shaft engages the teeth on a gear. Each time the shaft spins one revolution, the gear moves one tooth forward. If the gear has 40 teeth, you have a 40:1 gear ratio in a very small package. Here's one example from a windshield wiper. How Automatic Transmissions Work"