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Rear Trailing Arm

March 28, 2017

The rear trailing arms are a pair of sturdy metal links that connect the rear axle to the body (chassis) of a vehicle. They allow the axle to travel up and down freely, eliminate the need for leaf springs, and keep the axle in proper alignment to the vehicle.

Many aftermarket suspension kits for trucks use trailing arms because of the amount of control over the rear axle, increased wheel travel and durability. The term "three-link" or "four-link" indicates how many trailing arms the rear axle uses. Trailing arms don't typically wear out, as they have no moving parts, but the bushings that prevent wear on the trailing arms will wear out cause issues in the rear end of the vehicle, especially on lifted trucks.

Symptoms of a worn or failing rear trailing arm

  • Clunking from the rear axle: When placing the vehicle in drive or reverse, hitting bumps, accelerating, turning or braking, a bad trailing arm bushing will create a ‘clunk’ or ‘thud’ noise. The sound will get louds as the bushing deteriorates. If the bushings aren't changed, the trailing arm itself will eventually sustain damage.
  • The vehicle is unstable and won't keep to a straight line: When the bushings wear or the trailing arm breaks, the rear axle can move independently of the vehicle chassis. You'll notice this when hitting a bump, turning or holding the steering wheel in one position. The rear end of the vehicle may sway to one side over bumps or around turns, and while driving in a straight line, the rear wheels may change the direction of the vehicle.
  • Excessive and uneven rear tire wear: When the rear axle moves out of position, the vehicle has to drag the rear tires down the road or change the direction of the front tires. This results in a change in the direction the rear axle is pointing and causes the tires to wear on their new leading edge.
  • The vehicle is shorter on one side: The rear end of the vehicle may change height by up to about an inch. This is because the worn bushings allow the rear springs to lift that side of the vehicle slightly higher. Basically, it lengthens the trailing arm based on the amount of wear in the bushing.

Repair advice for a bad rear trailing arm

Though replacement of the entire trailing arm is rarely necessary, it may be less expensive to replace it with an entire new unit, rather than pay to replace the old bushings.

Replacing bushings in trailing arms can require a heavy-duty hydraulic press, a torch, or both, and there are many types of aftermarket bushings that claim better performance or a longer lifespan. Consulting a professional when deciding on replacement bushings is critical to longevity, and ensuring you know the entire procedure before beginning will prevent you from being stuck without the proper equipment to finish the job.

Cracked or bent trailing arms should be replaced. Driving with a cracked trailing arm could lead to separation of that side of the axle, and it's only a matter of time before further damage occurs.

When installing a lift kit on a vehicle, the trailing arms should be addressed. Changing the ride height of the vehicle also changes the angular position of the trailing arms, and can cause instability.

 

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