system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why don't cars have direct drive transmission instead of a gearbox?

Wouldn't direct drive be more efficient/less complex than an engine with a transmission?
gpt
A gasoline or diesel engine has an ideal speed that it wants to be running at. This is usually somewhere in the range of 1500-4000 revolutions per minute. But, the wheels of your car need to spin either slower or faster than that depending on what speed you want to go. So, a gear box lets your engine continue to run in its ideal range while the tires spin at a higher or lower rate.