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What Is Steering Linkage?

Feb 1, 2022 ·
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There are many different systems at work under the hood of a vehicle that help ensure people can get from one place to another safely. The steering system encompasses many parts that are all working to keep the vehicle traveling in the right direction when the steering wheel is moved.

The steering system also provides precise directional control of a vehicle chassis at varying weights to help minimize driver effort. This is especially important when driving semi-trucks and other heavy-duty vehicles.

The steering linkage is a component of the steering system that helps transfer motion from the steering wheel to the wheels on the vehicle and helps to turn them in the right direction at the correct speed. It is also integrated with the front suspension, steer axle, and wheel/tire components.

Several parts make up the steering linkage system in heavy-duty diesel vehicles. Keep reading to learn more about how they function.

Purpose of Steering Linkages

Steering linkage is a term used to describe a system of different pivots and connecting parts located between the steering arms and steering gear that moves the tires of a vehicle.

Steering linkages take the motion from the steering gear output and transfer it to the steering arms, which in turn send it to the wheels and allow them to turn in different directions. The system functions when a driver turns the steering wheel.

Steering Linkage Parts

Steering linkages feature a range of parts depending on which system is used, including the steering knuckles, steering control arm, tie rod ends, draglink, Pitman arm, and ball joints.

  • Steering control arm: Control arms are components that connect the draglink and steering knuckle on the driver’s side of a vehicle. When the draglink is moved in a straight line, the steering control arm moves the steering knuckle, which changes the angle of the steering knuckle.
  • Steering knuckles: Mounted to the front axle beam by steel pins also known as “kingpins,” steering knuckles allow the pivoting action required to steer the vehicle. The knuckles also contain a spindle where bearings and wheel hubs are mounted.
  • Ball joints: These components help form a connection between the steering control arms and steering knuckles. They allow the steering knuckles to have mobility. They play a key role in helping front wheels move back and forth, as well as up and down, and do not affect steering.

  • Tie rod ends: Tie rod ends are ball sockets that connect the control arms on each steering knuckle. They help transfer and synchronize the steering action of both steer wheels. Tie rods feature grease that works to cushion and protect the balls and sockets of the linkages as they move against each other.

Types of Steering Linkages

When it comes to heavy-duty steering linkage gear systems, there are three general types. They are the worm-and-sector, rack-and-pinion and recirculating-ball steering gear systems.

Worm and sector

The worm gearing used in these steering systems is slightly modified. The threads of the driving worm gear are meshed with the threads of a sector gear (via an input shaft). Rotating the input shaft transfers the rotary motion (via an output shaft) to the Pitman arm. The Pitman arm movement is transmitted through the draglink, to the steering control arm, then the steering knuckle, and finally to the wheels.

Rack and pinion

The rack-and-pinion steering linkage is the more common option seen on most cars, smaller trucks and SUVs. A semi-truck’s rack-and-pinion utilizes a vertical pinion gear, horizontal rack and power-assist system that helps translate the motion of the steering wheel into linear motion, which actuates the tie rods, turning the wheels on the vehicle. Freightliner introduced rack-and-pinion steering on its Cascadia chassis in 2007.

Recirculating ball

The input shaft of this type is also connected to the worm gear. However, the worm gear that’s used is straight. A ball nut mounted on the worm gear mates with it and has exterior teeth on one side that mesh with a sector gear. There are ball bearings located in the grooves between the ball nut and worm gear that transmit force when the steering wheel is turned.

As the ball turning the nut moves up and down, it causes the sector gear to rotate, which in turn causes the Pitman arm to transfer motion through the draglink, to the steering control arm, and the steering knuckle to turn the wheels.

Signs of a Worn Steering Linkage

If parts of a steering linkage start to wear out, you can experience a range of symptoms when you’re on the road. Some common signs of wear and tear can include:

  • Vehicle pulling to one side while driving
  • Irregular tire wear
  • Increased bumpiness and bouncing
  • Steering drifting during turns
  • Vibrations in steering wheel
  • Steering slipping when turning wheel
  • Knocking and clunking noises

Several of these symptoms are similar across many parts of the steering and suspension systems, so getting your vehicle inspected by a trained technician is important to help diagnose the source of the issue.

Learn About Steering Systems at UTI

Training on steering components, including linkages, is a key part of the Diesel Technology program offered at Universal Technical Institute.

The Diesel Truck Steering and Suspension Systems course covers how to inspect and service steering components. Students learn how to describe the types, steps of operation, and signs of wear and tear of different steering axles and linkages.

With total diesel technician employment expected to exceed 296,000 by 2030,48 it’s a great time to be exploring a career in the diesel industry. You can graduate from the Diesel program at UTI in as little as 45 weeks7 prepared for an entry-level position in the field.1

Want to learn more? Visit our program page or request more information today!

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1) UTI is an educational institution and cannot guarantee employment or salary.

2) For program outcome information and other disclosures, visit www.uti.edu/disclosures.

7) Some programs may require longer than one year to complete.

48) The U.S. Bureau of Labor Statistics projects that total national employment for Bus and Truck Mechanics and Diesel Engine Specialists will be 296,800 by 2030. See Table 1.2 Employment by detailed occupation, 2020 and projected 2030, U.S. Bureau of Labor Statistics, www.bls.gov, viewed November 18, 2021. UTI is an educational institution and cannot guarantee employment or salary. Updated on November 18, 2021.

Universal Technical Institute of Illinois, Inc. is approved by the Division of Private Business and Vocational Schools of the Illinois Board of Higher Education.

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