Gearboxes must be of the coaxial type with the pump, gearbox, and motor centerlines when included on vertical pump units, positioned vertically above each other to ensure an equal load distribution on the support ring.

Coaxial worm gearbox may be either of the epicyclic or multi-layshaft designs. It has been possible to combine the pump and the gearbox by mounting the impeller on the low-speed output shaft of the gear unit with recent epicyclic designs. In turn, reduces the overall height of the pump set leading to a more compact arrangement, this arrangement eliminates the need for one journal bearing.

In a wide range of speed ratios and load capacities, Gearboxes are available. Reducing or increasing speed is the purpose of a gearbox. As a result of the speed function, torque output will be the inverse. The torque output will increase if the enclosed drive is a speed reducer; the torque output will decrease if the drive increases speed. For the vast majority of gate drives, the speed is being reduced and hence the torque is increased. Thus in gate drive applications, Planetary gearbox is commonly called gear reducers. Gear drive selection factors include lubrication, speed ratio, shaft orientation, nature of the load, design type, environment, gear rating, operating temperature range, and mounting position.

The rotational speed of the rotor must be increased by the gearbox in a wind turbine drive train to match that required by the generator. Rotating at 3000 rpm or 1500 rpm, respectively, when synchronized to a 50 Hz grid Conventional generators for power generation are normally two-pole and four-pole machines.

With these conventional types of generator and taper bush, Very small wind turbines can rotate at speeds compatible and so the generator can be connected directly. However, to be able to match the speed of any form of conventional generator megawatt, larger class machines rotate much too slowly. The traditional solution in the drive train has therefore been to place a gearbox that by around 100 times will step up the rotational speed, for a typical megawatt-class wind turbine. On the turbine design, the precise ratio will depend.