The gearbox is a common component used with many applications. The most common known application is probably the gearbox used in your own car. A gearbox can adjust the speed by using different sizes of gears to mesh with another.

When looking at the pump application, the most often used type of gearbox is the parallel shaft helical gearbox. When a pump is constructed with a gearbox and an extra coupling, the pump can become quite long. To reduce the length, the flangemounted motor can be bolted to the side of the gearbox.

A gearbox is constructed with more than one ratio. The parallel shaft gearboxes are built with up to 4 ratios. This type of gearbox is suitable when discrete speed changes are acceptable and changes do not occur too often. This gearbox are changed manual and require the pump to be stopped first before changing gears. Because the gearboxes are made to order, the ratios are exactly as required, making it efficient as possible.

There are also semi-automatic gearboxes available. These gearboxes are normally used on portable engine driven pump packages. These gearboxes usually have more gears than the parallel shaft gearbox. The number of gears are over four and up to ten gears. A limited choice of ratios is available but the multiplicity of ratios compensate the lack an optimum ratio.

Usually the gearbox uses natural convention for cooling. When this isn't sufficient, the gearbox can be cooled by adding fans to the high speed shaft, or an external cooling circuit can be added for the lubricating oil. The gearboxes are sized by using service factors. The service factors are based upon the smoothness of the load and the drive.