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How the Mechanical Movement of a Manual Gearbox Works

Model: (Various brands) Various
Part: Transmission

Video tutorial

To describe what happens inside the gearbox, the synchronisers (the synchronisations) when the gearbox is in neutral are not engaged with any of the gear teeth. The primary shaft rotates, but power is not transmitted to the secondary shaft that goes to the wheels.

When you engage a forward gear (1st, 3rd, 5th), move the lever to the left and then forward, causing the selection fork to move the synchroniser collar towards the gear tooth of the desired gear, using friction to equalise the speed of the collar and the gear tooth.

Once synchronised, the teeth of the collar engage with those of the gear tooth, locking it to the shaft.

Power is now transmitted through this gear, determining the gear ratio. When engaging a reverse gear (2nd, 4th), the movement is "pull back and down", causing the collar to move in the opposite direction to engage the gear tooth.

For reverse gear, it often requires overcoming a resistance to prevent accidental engagement; this engages an additional gear that reverses the rotation direction of the shaft.


Posted on 17 May 2026 by ScegliAuto


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