Types of Gearbox and how they work

Gearboxes and the science behind them

4w ago


Function of a gearbox:

Gearboxes are made to increase or decrease the amount of torque that is given to the wheels. But giving more torque to the wheels does not mean that the wheels spin faster. On the contrary, it decreases the speed that the wheels receive.

This is due to the size of the gears in a gearbox. Increasing the size of the gear will produce a great amount of torque but will not provide speed. There are 5 gears in a normal car. Each of these gear has a gear ratio. This ratio is the size of the drive gear : the size of the gear. The drive gear is spinning by the help of the crankshaft that comes from the engine.

For example, the first gear, it is the largest gear in the gear box with a gear ratio of 1:10 and provides the largest torque. The drive gear(Pink gear) rotates the gears(Brown gear). Being the largest gear when in first gear the car drives the slowest but create a lot of torque. As the gears increase the ratio decreases until we reach 4th gear which has a ratio of 1:1. The gears after 4th are known as OVERDRIVE.

H-Type Gearbox:

A H-Type gearbox is the most common type of gearbox and it uses a H – patter to shifter the gears. It has gear arranged in pairs of 2 spikes connected to it. There are Synchros that get connected to the desired gear, these Synchros are attached to the output shaft rather than the gears. The spikes with the gears tightly connect to the Synchros, when the gear rotates the Synchros also rotate in turn spinning the output shaft. At the start there is a clutch that is basically a flywheel that spins while the gears are being shifted.

Sequential Gearbox:

Sequential Gearbox is what most of the sports cars and motorsports teams use. Unlike the H-type Gearbox, where you can go directly from 4th to 1st, the sequential gearbox cannot do that, instead you need to go through all the gear between 4th and 1st to reach first gear. It also uses a gearbox layout like a H-type gearbox, but the way of transition is different.

Torque Converter:

A torque converter is a Hydraulic system that completely removes the need of gearbox. It has three main components: Impellor, Stator, and the Turbine. The impellor it connected to the engine, giving it power to spin. The impellor contains fluid and has many fins. Once the impellor spins the fluid(due to centrifugal force) goes towards the Turbine. The fluid then spins the Turbine which is connected to the output shaft which rotate the wheels. But now the fluid is inside the Turbine which only spins because of the fluid which is sent from the impellor. That is why the Stator is used. It is confined to the centre of both the impellor and the Turbine. Once the fluid reaches anywhere near the centre, it is spun by the Stator. Like the impellor it also uses centrifugal force to send the fluid to the Impellor and then the whole cycle starts again.

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Comments (4)

  • Brilliant article. Well written and explains it all perfectly. Not always the case I come away from an article on DriveTribe having learnt something genuinely useful nowadays!

      26 days ago
  • I think if more people have known and understood how these things work, there would have been fewer so-called "drivers" who only know (or think they know) how to press two pedals.

      26 days ago
  • Just about everything in this article is incorrect or incomplete.

      16 days ago
  • Torque converter is not a gearbox. Jesus.

    It functions similar to clutch, to deliver power smoothly from engine to the rest of the drive train. The reason why auto trans doesn't stall when you brake is the presence of torque converter. But now it becomes more and more obsolete as mechatronics is becoming more advanced, and clutch can be electrically adjusted without ending up like Saab Sensonic.

      19 days ago