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Power Steering Systems

Types of Steering Systems

There are two main types of steering systems. They are manual and power. Manual is rarely used, if at all, any more. Power systems are found on the majority of vehicles today. There are two main types of power steering systems. One is conventional and the other is rack and pinion. Either system allows the driver to control the vehicle direction.

Conventional

The conventional system is divided into two portions, mechanical and hydraulic. These two parts work together to make the steering the vehicle easy for the driver. The following components are found in a conventional system:

Mechanical

  • Steering wheel
  • Steering column
  • Upper steering shaft
  • Steering shaft coupler
  • Lower steering shaft
  • Steering gear
  • Pitman arm
  • Drag link
  • Idler arm
  • Inner tie rods- two
  • Tie rod adjusting sleeves
  • Outer tie rods- two
  • Steering knuckle

Hydraulic

  • Fluid
  • Fluid reservoir
  • Pump supply hose
  • Pump
  • Pressure hose
  • Cooler supply hose
  • Cooler
  • Cooler return hose

Steering Wheel

The steering wheel in the device the driver uses to turn the vehicle in the direction they wish to travel. Some wheels have controls for other systems on them. The other systems may be the radio, cruise control and horn. On most cars a driver air bag is found in the middle of the wheel and may be marked with a “SRS” or “airbag” impression.

Steering Column

The steering column is what the steering wheel is attached to. The column may have controls for other systems mounted to it. These systems may be the windshield wipers and washer system, turn signals, cruise control, steering column position adjuster, and ignition key cylinder. All of these controls make access and use of these systems easy for the driver. Other components may be found on the steering column such as the airbag sliding contact, also known as the clock spring, and ignition switch.

Upper Steering Shaft

The upper steering shaft transfers the motion of the steering wheel to the lower steering shaft. It is connected at the base of the steering column and runs down toward the firewall and connects to the steering shaft coupler.

Steering Shaft Coupler

The steering shaft coupler is a joint that allows the upper steering shaft to connect to the lower steering shaft. The coupler also allows the shaft to rotate at an angle. It is usually located just before the firewall inside the vehicle. This coupler can be unfastened. The purpose of being able to loosen this coupler is to make removal of the steering column easy.

Lower Steering Shaft

The lower shaft is a continuation of the upper steering shaft. It can be found under the hood coming from the firewall and connected directly to the steering gear input shaft. The lower steering shaft is collapsible. In the event of an accident the steering shaft will collapse and shorten before breaking or poking through the firewall.

Steering Gear

The steering gear is a box that contains gears that change the turning ratio of the steering wheel to the wheels. This gear transfers the rotational motion of the steering wheel into a left and right motion to make the front wheels turn. It is usually located on the left front frame rail. In power steering systems, the steering gear is assisted hydraulically. This makes it easier to turn the steering wheel.

Pitman Arm

The pitman arm is a short connector that transfers the movement from the steering gear output shaft to the drag link. It usually bolts directly to the steering gear on one end. The other end usually has a ball joint stud that goes through the drag link and is held to the drag link with a nut.

Drag Link

The drag link transfers the turning motion to both front wheels. This link may be made of steel and is generally about one inch thick. The inner tie rods are attached to each end of the drag link.

Idler Arm

The idler arm supports the drag link on the right side of the vehicle. It is usually attached to the right front frame rail. The idler arm passes through the drag link and is fastened to it in the same manner as the pitman arm.

Inner Tie Rods

The inner tie rods are joints that pivot and transfer the turning motion to the wheels. They are bolted through the drag link on one end. The other end is threaded into the tie rod adjusting sleeve. These are found on each side of the drag link.

Tie Rod Adjusting Sleeves

The tie rod adjusting sleeves connect the inner and outer tie rods. They usually have right hand threads on one side and left hand threads on the other. This is necessary to allow the toe setting of the wheels to be adjusted.

Outer Tie Rods

The outer tie rods connect the tie rod adjusting sleeve to the steering knuckle. They serve the same purpose and function the same way as the inner tie rods.

Steering Knuckle

The steering knuckle brings together the steering and suspension system. It is mounted using the control arms, struts, and ball joints from the suspension system and is where the outer tie rods connect. The steering knuckle can be made from steel or aluminum. It is on the knuckle that the wheel hub is attached and the wheel is mounted.

This concludes the mechanical portion of the conventional steering system. The items that follow are parts that form the hydraulic portion. The following components are what make it easy for the driver to turn the steering wheel. These components collectively provide what is referred to as power steering assist.

Fluid

Fluid is what allows the mechanical parts of the system to move easily. The fluid works with the pump to provide power assist. Check with your manufacturer or consult your owner’s manual for the proper type of fluid to use in your vehicle’s system.

Fluid Reservoir

The fluid reservoir is the container that holds the fluid and supplies it to the pump. This is where the level of fluid is checked and added. The reservoir can be remotely mounted or in older vehicles, be a part of the power steering pump itself.

Pump Supply Hose

The pump supply hose allows fluid to travel from the reservoir to the pump.

Pump

The pump is what provides the steering assist to the driver. Pumps may be designed in one of several ways. It is usually driven by a belt on the front of the engine. In any case it moves the fluid through the entire system. The fluid will usually pass though a specially designed valve that contains a restriction. This valve is typically located in or on the pump or rack. When the fluid passes through the restriction it becomes pressurized. The fluid, pump, and restriction creates power steering assist.

Pressure Hose

This hose supplies the steering gear with the pressurized fluid from the pump. It may be made of a combination of steel and rubber.

Cooler Supply Hose

This hose allows the fluid to exit the steering gear and flow to a cooler. On vehicles without a cooler, this hose will return the fluid to the reservoir. If this is the case, this hose will be the return hose instead.

Cooler

The cooler allows the fluid to cool down and maintain an ideal temperature range. It may have fins similar to a radiator that allow the heat to dissipate quickly. The cooler is generally mounted toward the front of the vehicle in front of the radiator.

Cooler Return Hose

The cooler return hose allows the fluid to exit the cooler and return to the reservoir. It may be made of rubber and molded to fit specific contours to be routed properly.

This concludes the description of the conventional power steering system.

Rack and Pinion

Rack and pinion steering is a simplified version of the conventional steering system. It provides the exact same results using most of the same components. The major difference is instead of a steering gear, a rack and pinion style gear is used and the lower steering shaft, pitman arm, idler arm, drag link, and tie rod adjusting sleeves have been eliminated. This allows a better “feel” and response for the driver.

The components of a rack and pinion system are:

Mechanical

  • Steering wheel
  • Steering column
  • Upper steering shaft
  • Steering shaft coupler
  • Rack and pinion gear
  • Inner tie rods- two
  • Outer tie rods- two
  • Steering knuckle

Hydraulic

  • Fluid
  • Fluid reservoir
  • Pump supply hose
  • Pump
  • Pressure hose
  • Cooler supply hose
  • Cooler
  • Cooler return hose

The following is a description of the components in a rack and pinion steering system that are different from those in a conventional power steering system.

Rack and Pinion

The rack and pinion gear, commonly referred to as the rack, performs the same function as the steering gear. It contains two gears that change the rotation of the steering wheel into lateral movement to turn the wheels left or right. The name comes from the types of gears located inside the rack and pinion unit. The pinion is the gear that turns with the steering wheel. It rotates like a clock. The term rack is used for the gear that the pinion meshes with. The rack looks like a long straight gear; kind of like a stubby comb. The pinion rotates with the motion of the steering wheel and the rack moves left or right respectively. This motion is transferred to the other components and finally the wheels. The rack and pinion unit can be mounted close to the firewall or in front of the subframe on a vehicle. The lower steering shaft is not needed because the steering shaft coupler is attached directly to the rack and pinion input shaft. The rack is usually held in place with two big bolts.

Inner and Outer Tie Rods

The inner and outer tie rods function the same way on a rack and pinion system as they do in a conventional steering system. They provide the mechanical link from the rack to the wheels. These tie rods have a ball and socket joint that allows them to pivot. The inner tie rods thread directly onto the rack. This connection is made inside of the bellows boot on each end of the end of the rack. The outer tie rods thread directly onto the inner tie rods on one end and connect to the steering knuckle on the other end. The inner tie rods have a lock nut on the threaded portion that holds the outer tie rod in place. This lock nut is loosened to adjust the toe setting when performing an alignment.

Conclusion

As you can see the main difference between a conventional power steering system and a rack and pinion system is the design of the steering gear and fewer mechanical components. The other components function the same way in both systems.

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