A gearbox, also known as a gear case or gear head, is a gear or a hydraulic system responsible for transmitting mechanical power from a prime mover (an engine or electric motor) into some form of useful output.
A gearbox is a set of gears for transmitting power from one rotating shaft to another. They are used in a wide range of industrial, automotive and home machinery application.
Gear heads are available in different sizes, capacities and speed ratios. Their main function is to convert the input provided by an electric motor into an output of lower RPM and higher torque.
Functions of a Gearbox
A gearbox is precisely bored to control gear and shaft alignment.
It is used as a housing/container for gear oil.
It is a metal casing for protecting gears and lubricant from water, dust and other contaminants.
Gearbox Specifications
There are a number of performance specifications which must be considered while choosing a gearbox for different industrial applications. Some of the important specifications are :
Gear ratio : The ratio may be specified as x : 1, where x is an integer.
Output torque
Maximum input power
Maximum input speed
Gearing arrangement
Reducer output
Shaft Alignment
The Gearbox (Transmission)
Types of gearing:
Various types of gearing are used on a motor vehicle. The gearboxes employ one or more of the following:
1- Spur, teeth parallel to axis, used on sliding mesh.
2- Helical, teeth inclined to axis to form helix.
3- Double helical, two sets of opposing helical teeth.
4- Epicyclic or planetary, spur or helical gears rotating about centers which are not stationary.
Gear ratio (single gear train):
The gear ratio, or velocity ratio, between a pair of gear wheels is in inverse ratio to the number of teeth on each. Thus:
NB/NA = DA/DB= nA/nB
NB = NA (nA/nB)
Where:
NA= rev per min of gear A, nA = number of teeth on A
NB = rev per min of gear B, nB = number of teeth on B
DA = Diameter of gear A
DB = Diameter of gear B

1. A gearbox is a method of transmitting energy from one mechanical device to another. It works by increasing the torque while at the same time reducing the speed. Torque generates power by twisting and bending solid material. The gearbox is located in the power shaft, and every gear in the gearbox has a specific purpose in the operation of the vehicle. Each level of speed has a relative gear that gives your vehicle the right amount of speed and torque. A gear ratio is used to determine the level of force in each gear, and once this ratio is set, it cannot be changed.

Manual
A manual gearbox works when the clutch is pressed down. This allows the gearshift to be put into any desired gear. Most manual transmissions have five or six gears in their gear box.

When the gears in the gearbox are shifted into a higher gear, the gearbox gives the vehicle more power while using less fuel. This works because the gearbox rotates the drive shaft, alternating the torque and power.

When the gears are shifted into a lower gear, your vehicle will run at a lower speed. Gears engage the drive shaft at different points along the way. When the gear is lower, it will engage the drive shaft closer to the gearbox.

Automatic
An automatic transmission's gearbox works in concert with the accelerator, brakes and drive shaft. The transmission in an automatic vehicle is more expensive and can be more difficult to maintain and replace. Automatic transmissions use the programmed gear ratio, and spin the drive shaft according to how much power is coming from the accelerator. When the brake in the vehicle is applied, the gearbox decreases the speed by using counterweights to slow the drive shaft.