The power steering pump is a belt-driven or electric-driven hydraulic pump that generates the hydraulic pressure needed to provide power steering assist. It develops output pressures of 1,000 PSI or more. The pump output is directed to the steering gear, often a rack and pinion type unit, where the hydraulic pressure pushes on the steering rack, greatly reducing the effort it would otherwise take to turn the steering wheel. To ensure that you get the correct pump, it is best to check the size and shape of the one currently installed so you can compare with the listed pumps. Some important information for selecting the correct power steering pump is the type of pump needed, operating mode (hydraulic or electric), pulley compatibility (pulley diameter, number of ribs) and date limitation of the unit. As car manufacturers regularly update certain peripherals and design of their models, some power steering pumps will only be suitable for particular models of certain years.