Eli5: What is the purpose of downshifting for a semi-truck and how does it work?

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I have always wondered what those loud noises are the semi-trucks make as they appear to be slowing down, but I don’t understand how that helps?

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24 Answers

Anonymous 0 Comments

Ok like you are 5:

An engine wants to not turn. It wants to just sit there. Normally adding gas and spark causes little explosions inside the engine, which force it to turn and move the truck.

When you stop adding gas to the engine it slows down as fast and as much as it can. If it is connected to the wheels of the truck (in gear, clutch disengaged), it will slow down the truck as well. Which gear the driver has the truck in will determine how effective the engine can slow the truck down, lower gears working better (and being louder).

I read the assignment.

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