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Rear Trailing Arm

The rear trailing arms are a pair of sturdy, metal links, which 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, increase in wheel travel, and durability.  The term ‘3-link’ or ‘4-link’ signifies how many trailing arms the rear axle uses. Trailing arms do not typically wear out, as they have no moving parts, but the bushings that prevent wear on the trailing arms wear out after a while and begin to cause issues in the rear end of the vehicle, especially on lifted trucks.

Symptoms of Wear or Failure of the Rear Trailing Arm

  • Clunking from the rear axle: when placing the vehicle in drive or reverse, hitting bumps, accelerating, turning, or braking, the trailing arm will alert you to bushing failure with a ‘clunk’ or ‘thud’ that increases in intensity as the bushing further deteriorates. If the bushings are not changed, damage resulting in replacement of the trailing arm is eminent.

  • The vehicle is unstable, and cannot maintain a straight line: when the bushings wear, or the trailing arm breaks, the rear axle can move independently of the vehicle chassis. This becomes evident 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 is allowed to move out of position, the vehicle must now drag the rear tires down the road or change the direction of the front tires. This results in alteration of the rear thrust ange (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: there may be a height difference of the rear end of the vehicle, even 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 by the amount of wear found in the bushing.

Related Repair Advice on the Rear Trailing Arm

  • Though replacement of the entire trailing arm is seldom required, it may be more cost effective to replace with a new unit, rather than pay for the old units to have bushings replaced.

  • 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 lifetime. These being the case, 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 changed immediately. Driving with a cracked trailing arm could lead to separation of that side of the axle, and, generally speaking, if the vehicle is used in a manner that causes a trailing arm to crack or bend, it is only a matter of time before further damage occurs.

  • When installing a lift kit on a vehicle, for trucks or cars, 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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