What Is Steering Linkage?

Key Points

• Understanding Steering Linkage Systems:Steering linkage is a crucial component of a vehicle's steering system, transferring motion from the steering wheel to the wheels and ensuring the vehicle travels in the intended direction. It is integrated with the front suspension, steer axle and wheel/tire parts, providing precise directional control and minimizing driver effort, especially in heavy-duty vehicles like semitrucks.
• Historical Evolution of Steering Systems:The concept of steering has evolved significantly since Carl Benz's manual steering in the earliest cars. Power steering was introduced by George Fitts in 1876, with significant improvements over the years, including Frederick W. Lanchester's hydraulic design and Francis W. Davis' electric power steering (EPS) system. By the 1950s, EPS systems became more common in vehicles, making manual steering nearly obsolete.
• Components of Steering Linkage:Key parts of the steering linkage system include the steering wheel, steering control arm, steering knuckles, ball joints and tie-rod ends. These components work together to transmit the driver's input from the steering wheel to the vehicle's front wheels, allowing for controlled and synchronized movement.
• Types of Steering Linkage Gear Systems: There are three main types of steering linkage gear systems: worm-and-sector, rack-and-pinion and recirculating-ball. Each type has its unique mechanism for transferring motion from the steering wheel to the wheels, with rack-and-pinion being the most common in cars, smaller trucks and SUVs.
• Identifying and Addressing Faulty Steering Linkage: Common symptoms of a faulty steering linkage include the vehicle pulling to one side, irregular tire wear, increased bumpiness, steering drifting during turns, vibrations in the steering wheel and knocking noises. Regular inspections, adjustments and lubrication are essential for maintaining the steering linkage system, and professional help is recommended for repairs to ensure safety and proper functionality.

Under the hood of a vehicle, many systems work to ensure people can travel safely.

This includes the steering system. But what is steering linkage and why does it matter in vehicles?

Steering linkage systems consist of many parts that keep the vehicle traveling in the intended direction when the steering wheel is moved.

It’s a critical part of truck mobility. If you’re interested in diesel technology and want to learn the fundamentals, you can start by learning about steering linkage systems and how they help get people from Point A to Point B.

Keep reading to learn more!

What Is a Steering Linkage System?

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 parts.

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 semitrucks and other heavy-duty vehicles.

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.

Read: How Do Tractor AC Systems Work?

History of Steering Linkage

Carl Benz, a German engine designer and automotive engineer, applied for a patent in 1886 to officially invent what we now call the earliest cars. They had manual steering, which was much more difficult to operate than the current motorized steering power that allows us to travel with far less elbow grease!

Power steering was invented in 1876 by George Fitts, an American engineer. In 1902, Frederick W. Lanchester, an English engineer who began his automotive projects as a hobby before developing a car company, improved power steering with a new hydraulic design. American engineer Francis W. Davis in 1926 invented the earliest version of a power steering system that could fit in a car: an electric power steering (EPS) system.

However, automotive manufacturers didn’t adopt these evolving steering blueprints until the 1950s, when Chrysler implemented the first EPS system in an automotive system available for consumer purchase. From that point on, EPS systems started to be incorporated across a variety of vehicles until manually powered steering became essentially obsolete!

Read: Everything You Need to Know About Heavy-Duty Truck Alignment

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, Pitman arm and ball joints.

• Steering wheel:A vehicle's steering wheel is a mechanical input device connected to the steering column, which is connected to the vehicle's front wheels via a system of linkages and gears. When the driver turns the steering wheel, rotational motion is transmitted to the steering column, which delivers angular displacement to the front wheels and allows the driver to control the vehicle's direction.
• Pitman arm:A Pitman arm connects the steering gear box to the steering linkage. It translates the rotary motion from the steering gear into linear motion, allowing the wheels to turn. This component is essential for converting the driver's steering input into the movement needed to guide the vehicle's direction.
• Steering control arm: Control arms are components that connect the drag link and steering knuckle on the driver’s side of a vehicle. When the drag link 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 needed 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 move. 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 sync the steering action of both steer wheels. Tie-rods feature grease that works to protect the balls and sockets of the linkages as they move against each other.

What is a drag link?

A drag link converts rotary motion from a crank arm to a second bell crank. It connects the Pitman arm with the tie-rod ends to facilitate the motion needed for turning a vehicle.

Drag links help ensure the vehicle's wheels turn when prompted by the driver at the wheel, acting as a bridge between the steering gear and the wheels.

A faulty drag link can lead to poor handling, misaligned wheels, excessive vibration, also known as the “death wobble,” and uneven tire wear.

While drag links are on most vehicles, some steering linkage systems remove the need for one.

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. This type of steering linkage doesn’t have a drag link or Pitman arm.

A semitruck’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 to turn 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 drag link, to the steering control arm and the steering knuckle to turn the wheels.

Read: How Does a Diesel Engine Work?

Common Symptoms of Faulty 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 faulty steering linkage symptoms 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.

FAQs

Are the steering components of a truck different from those of a car?

Absolutely, there are differences between truck steering linkage parts and steering components of a car. Due to their weight, trucks need more torque to turn the front wheels, resulting in a larger steering wheel for greater leverage and often include additional components like a steering stabilizer.

Are there specific maintenance requirements for steering linkage parts?

Yes, there are a few maintenance requirements for steering linkage parts. They need regular inspections and adjustments to compensate for wear. Lubrication is also key to prevent premature wear out and undue strain on the system.

Can I replace the steering linkage components myself or should I seek professional help?

Steering linkage system repairs and replacements can be complex jobs! Getting it wrong could lead to serious safety issues. Unless you've got the right experience and skills, it might be best to let a pro handle this one.

Are there safety concerns associated with a damaged steering linkage?

Yes, there are serious safety concerns with a damaged steering linkage. Most notably, if it fails, you could lose control of your vehicle, which could lead to an accident.

Read: How Do Truck Suspension Systems Work?

Learn About Steering Linkage Systems at UTI

Training on steering components, including linkages, is a key part of the 45-week Diesel Technology program offered at Universal Technical Institute.^1,7

The Diesel Truck Steering and Suspension Systems course covers how to inspect and service truck steering linkage 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 308,000 by 2033, it’s a great time to be exploring a career in the diesel industry.⁴⁸ Want to learn more? Request more information to talk to an Admissions Representative!

UTI Campuses That Offer Diesel Mechanic Training

• Avondale, Arizona
• Long Beach, California
• Rancho Cucamonga, California
• Sacramento, California
• Austin, Texas
• Dallas/Fort Worth, Texas
• Houston, Texas
• Bloomfield, New Jersey
• Exton, Pennsylvania 
• Lisle, Illinois
• Miramar, Florida
• Orlando, Florida