I tried looking online but have a hard time finding out exactly what the number on the gears of the car represent. What’s the difference between 1-3 or 2-5?
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They are the gears, in order, from 1-5. So you shift left up (if you are American or European) for one, left down for 2, center up for 3, center down for 4, right up for 5, and right down for 6 if you have six gears. To get in reverse you normally have some trick so you don’t accidentally put it into first instead of reverse.
The numbers don’t really represent anything other than the lowest gear is 1 and the highest is the nth. The actual gear *ratios*, which is the speed of the output shaft of the transmission divided by the speed of the input shaft.
In a simplified transmission, the *output* of the engine is the *input* of the transmission. The *output* of the transmission is what turns the driving wheels. So, if I need to drive the wheels slower than the engine, I gear it down. Typically gears 1-4. Now I want to drive the wheels *faster* than the engine, that is overdrive.
The reason we need this scheme is that a car engine only makes torque in a very narrow band of RPMs. So I might need a really high torque at slow speed, like towing something heavy from a dead stop up a hill. In that case, I need the engine to rev up to 4500 RPM but I only want the wheels to turn whatever RPM equals 5-10 mph. I might need relatively low torque at a higher speed, like highway driving where I only need enough power to overcome wind resistance/gravity/traction. I don’t need that much torque, so I can slow down the engine but I need to keep the wheels fast.
You can ‘gear up’ a car simply by putting larger diameter wheels on the car, or gear it down by putting smaller wheels. It is the same basic principle, you measure speed by how many RPMs the wheel goes in a given amount of time. If your circumference is 100 centimeters, one RPM will equal 100 cm. A wheel that is 50 cm will only go 50 cm for one RPM. If those wheels both ran for ten seconds each with the same input RPM, the bigger wheel will be a farther distance away after 10 seconds, therefore it went faster. The input RPM didn’t change, the output speed (the distance measured along the circumference) *did change*.
A more technical definition of gear ratios is actually the number of teeth in the gear, more teeth means more diameter which means it is a bigger gear. A smaller number of teeth is a smaller gear. You can look at a Bicycle gearset, those are technically sprockets but it is the same idea. Assume one ring in the front and 9 in the back. The lowest gear is the rear chain ring with the fewest number of teeth and that would be 1. The 9th gear is the ring with the largest number of teeth and is the highest gear.
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