There are typically three types of hydraulic pump constructions found in mobile hydraulic applications. These include gear, piston and vane; however, there are also clutch pumps, dump pumps and pumps for refuse vehicles such as dry valve pumps
The hydraulic pump is the component of the hydraulic system that takes mechanical energy and converts it into fluid energy in the form of oil flow. This mechanical energy is taken from what is called the prime mover (a turning force) such as the power take-off or directly from the truck engine.
With each hydraulic pump, the pump will be of either a uni-rotational or bi-rotational design. As its name implies, a uni-rotational pump is designed to operate in one direction of shaft rotation. On the other hand, a bi-rotational pump has the ability to operate in either direction.
SAE AA—3 1/4" Mounting Hole Center-to-Center
SAE A—4 3/16" Mounting Hole Center-to-Center
SAE 4F17—2" Mounting Hole Center-to-Center