You know that gear stick that we all use so much? Well, I know what it does in the sense that I know how to change gear and drive a car with a manual gearbox, but I don't know much more than that.

  • What exactly is a gearbox?
  • What does it look like (a diagram, animation or picture would be helpful here)?
  • What happens underneath the gear stick when I move it around with the clutch pedal down?
  • How does the gearbox (transmission?, gear train?) connect to the clutch (or anything else for that matter)?

1 Answer 1


Here's a link to an article that describes what you're looking for in detail.


What the gearbox does is allow the engine to run at the RPM range that it is most happy, while allowing your wheels to run at the speed which you desire. It does that through a collection of gears who's ratio determines how fast the wheels turn for a given engine speed.

All of the following comes from the article on transmissions.

A simplified transmission

The green shaft comes from the engine and spins at engine speed as long as the clutch allows the engine to be connected to it.
All the gears on the red shaft spin together.
All the blue gears on the yellow shaft are mounted on splined gears so they can shift back and forth.

The purple collar is attached to the gear shift knob, which changes which blue gear is attached to the red gears. This example is only a two speed transmission, but it's the same principle for any manual transmission.

The clutch is the device that connects and disconnects the engine from the rest of the transmission. This allows the gears to be changed without that wonderful grinding noise you mentioned. That grinding is cause by the gear ratio you have selected not matching the engine speed to the wheel speed very well. This happened a lot more before syncromesh which is a system for bringing the gears together gradually rather than slamming them together. The slamming required you to manually get the engine RPM correct with the gas pedal to match the engine RPM to car speed through the gear you selected. If you missed on the RPM, you got the crunch. Synchromesh brings the gears together gradually, allowing the two gears to find each others speed without you having to get it exactly right with the throttle.

Back to the clutch, here's a photo of one from another linked article

Interior of a manual transmission showing the clutch (far left)

The clutch plate is the disk with the springs on it all the way to the left. The clutch plate is two plates that are connected together in such a way that they can slide over each other for a short distance. The springs keep the plates together, but when the engine is first connected to the gears (by letting out the clutch pedal) the springs compress to put some give in the system and prevent a lurching forward as the connection is suddenly made. The clutch sits between the engine and the green shaft in the first picture, allowing the driver to connect the engine to the wheels or not, via the clutch pedal.

Link to the article on clutches for more info: http://auto.howstuffworks.com/clutch.htm?utm_source=Outbrain&utm_medium=Referral&utm_campaign=OutbrainOrganicTraffic=obinsite

I think that was all the parts of your question..
Hope that helps!

  • We definitely appreciate you being here! You really need to flesh out your answer. Link only answers (which this is) will more than likely get downvoted if not deleted. Grab some pictures and explain away. Use the link if you need to to back up what you are tying to say :D Jan 15, 2016 at 19:46
  • Oh! I was not aware of that, my apologies. I figured the article explained it rather well so why reproduce it here but I see your point. I will edit it to include way more info. Thanks for letting me know!
    – cdunn
    Jan 15, 2016 at 19:51
  • 1
    @cdunn This answer has already much improved. Keep up the good work! I think the idea is to create a sort of central repository that has very good SEO (which SE certainly does). Reproducing a summary here also will inform most readers of the most important and relevant information with respect to the question at hand. Jan 15, 2016 at 19:58
  • I had not thought about that, I like that idea a lot. And you have a very good point, the net is changing constantly so having a repository solves the broken link problem. That's great info, thanks!
    – cdunn
    Jan 15, 2016 at 20:07
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    @DucatiKiller Me too. I like having the combination of the simplistic diagram to get the idea of how it works, and then add the cutaway to see what they really look like in a working system.
    – cdunn
    Jan 15, 2016 at 20:55

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