What is a Drag Link?
Found on heavy-duty vehicles like semitrucks, buses and other commercial vehicles, a drag link is part of the steering linkage that connects the steering wheel to the front wheels. Also known as a center link, drag links ensure that the front wheels move in the same direction. Without the drag link, steering would be impossible.
What Does a Drag Link Do?
Important for maintaining proper steering alignment and control, the drag link works with other steering and suspension components like control arms and tie rods. A steel shaft running across the front of the vehicle, the drag link attaches the steering gear to the steering knuckle and transfers movement from the Pitman arm to the tie rod end. When the driver turns the steering wheel, the drag link takes that steering input and transfers it to the wheels to allow the vehicle to turn in the right direction.
What Are the Symptoms of a Bad Drag Link?
If the drag link is damaged or worn, it can result in handling issues, steering instability and uneven tire wear. Be on the lookout for these signs of a failing drag link.
Poor Handling
A failing drag link can cause the connection between the wheels and steering wheel to become loose. If this happens, the steering and handling can feel unstable, leaving the driver feeling not in control when turning or traveling at higher speeds.
Vehicle Pulls to One Side
A faulty drag link can cause the wheels to come out of alignment which can lead to the steering to feel like it is wandering. It can also cause the vehicle to slightly turn even when the steering wheel is straight which results in the steering not being as precise as the driver is used to.
Excessive Vibration
A bad drag link can cause the wheels, steering wheel and chassis to vibrate excessively. Traveling at high speed may lead to the whole vehicle shuddering.
Uneven Tire Wear
A faulty drag link can cause one tire to point in a different direction. Increased or uneven tire wear is a result of the misalignment that a failing drag link causes.
What Causes a Drag Link to Fail?
Besides normal wear and tear, drag links can fail due to the compressive loads that heavy-duty trucks, semitrucks and other commercial vehicles haul. The stress can cause the tubes to buckle. Driving over potholes or rough roads can put stress on the drag link which cause it to prematurely fail.
How to Diagnose a Failing Drag Link
Because many of the symptoms of a failing drag link are common to other steering and suspension components, diagnosing a failing drag link calls for a physical examination, test drive and other steps.
Visual Examination
Do a visual inspection checking for damage, wear or rust. Look for missing bolts, nuts, cotter pins and damaged sealing boots.
Check for Play
Move the drag link back and forth looking for excess play. Minimal movement is normal; excessive play is an indication of a worn part.
Tires
Inspect the tires for signs of uneven tire wear patterns.
Steering Wheel Test
Inspect the tires for signs of uneven tire wear patterns.
Test Drive
Take the vehicle for a ride and listen for clunking or knocking sounds when turning.
When Should Drag Links Be Replaced?
While drag links may need to be replaced every 50,000 to 100,000 miles, what you drive, where you drive and how you drive can have a direct effect on the lifespan of drag links.
Vehicle Type
The drag link on trucks and SUVs that haul heavy loads may experience premature wear due to the extra stress that carrying extra weight can cause. Performance vehicles that are pushed to the limit may also experience premature drag link failure.
Road Conditions
Traveling over roads filled with potholes, bumps and other road hazards can cause drag links to wear out faster.
Driving Habits
Aggressive driving habits like sudden stops, hard cornering and fast acceleration can put additional stress on drag links and other steering components.