The rack and pinion gear is a fundamental component in a vehicle steering system, converting the rotational motion of the steering wheel into linear motion to turn the wheels. The system consists of a pinion gear, which is attached to the steering shaft, and a rack gear, which is connected to the steering arms. As the pinion gear rotates, it moves the rack back and forth, translating the driver steering input into the precise movement of the wheels. This setup provides direct, responsive steering with minimal backlash.

The hydraulic rack and pinion gear combines the traditional rack and pinion mechanism with hydraulic assistance to enhance steering performance. This system includes hydraulic pistons that assist in moving the rack, reducing the effort required from the driver and providing smoother, more responsive steering. The hydraulic power is typically supplied by a pump driven by the engine, which helps to improve maneuverability, particularly at low speeds or when parking.