What is the gearbox ?

The gearbox is the second element of the power train in an automobile. It is used to change the speed and torque of vehicle according to variety of road and load condition. A gearbox changes the engine speed into torque when climbing hills and when the vehicle required. Sometimes it is known as torque converter. Main functions of a gearbox is as follow:

  1. Provide the torque needed to move the vehicle under a variety of road and load conditions. It does this by changing the gear ratio between the engine crankshaft and vehicle drive wheels.
  2. Be shifted into reverse so the vehicle can move backward.
  3. Be shifted into neutral for starting the engine.

The components of any gearbox are:

  1. Counter shaft
  2. Main shaft
  3. Gears
  4. Bearings


In a gearbox, the counter shaft is mashed to the clutch with a use of a couple of gear. So the counter shaft is always in running condition. When the counter shaft is brought in contact with the main shaft by use of meshing gears, the main shaft starts to rotate according to the gear ratio. When want to change the gear ratio, simply press the clutch pedal which disconnect the counter shaft with engine and is then connected to the main shaft with counter shaft by another gear ratio by use of the gearshift lever. In an gear box, the gear teeth and other moving metal must not touch. They must be continuously separated by a thin film of lubricant. This prevents excessive wear and early failure. Therefore a gearbox runs partially filled with lubricant oil.