Long Live the King Pin—With Maintenance and Proper Repair
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Long Live the King Pin—With Maintenance and Proper Repair

Sponsored by DANA Incorporated

A “king pin” may be defined as “a thing essential to the success of an operation,” so it’s no surprise that the steer axle king pin in a commercial vehicle is a supremely significant part. Proper maintenance is the key to prolonging the life of the crucial king pin, but no part lasts forever. When king pin wear occurs, get the labor-intensive replacement job done correctly the first time with a kit that provides high-quality parts and ease of installation.

King pins, the bushings that encircle them, and their related components are essential for proper steering. The king pin on a truck connects the steer axle to the steering knuckle, supporting the steering geometry and allowing the wheel ends to turn the vehicle. These hefty steel pins work in tandem with the bushings to handle intense forces while keeping the knuckle in proper alignment.

Signs of king pin wear or damage include uneven front tire wear, incorrect vehicle alignment, and a pull in the steering. If a worn king pin is ignored, or a repair is not completed thoroughly, the result can be costly structural repair. For example, a loose king pin in an axle can eventually necessitate replacing the entire axle. Especially when managing a fleet, costs like that accumulate quickly. There are two main causes of king pin wear: poor maintenance practices and damage due to an accident. However, by far the most frequent cause for king pin wear is lack of maintenance.

With proper maintenance, a layer of grease ensures that the king pin does not make contact with the bushings. Less-than-ideal grease intervals or use of the incorrect grease will cause the protective layer of grease to break down, and the interior of the bushing will begin to erode due to the metal-on-metal contact. Maintaining proper lubrication is the key for the long life of the parts and the system overall.

In addition to regular lubrication, it’s a good idea to check for steer axle king pin problems every time a truck is on a lift. Use a dial indicator to check for end play and keep a log of the findings. This end-play log will serve to indicate when part replacement becomes necessary, and it can help prevent premature tire wear. That’s because a worn king pin allows for too much end play in the tires; it’s much more efficient to detect a worn king pin by keeping a log than by observing fast-wearing tires.

Even with correct maintenance, king pins are not indestructible. A king pin will likely need to be replaced one time in the lifespan of a truck. If part replacement is called for, a king pin kit that is specific to the axle model—and that contains all the components required to refurbish the axle and the steering knuckle—can help with this demanding task. Replacing all of the worn parts at the same time, including the bushings, seals, shim pack, thrust bearings, and king pins, will help avoid further downtime later. Spicer® offers all-makes kits that are designed to deliver a significant performance advantage, provide easy installation, and that meet OE specifications. With a king pin kit from Spicer, technicians can be assured that the components they’re installing meet Dana’s rigorous standards for quality.

King pin wear is inevitable, but following preventive maintenance practices will prolong part life. By adhering to regular grease intervals, tracking end play, and replacing worn parts promptly, you can reduce downtime, save money, and calculate future repair needs. When it is time for a replacement, a king pin kit can help the time-consuming and potentially frustrating process go by as smoothly as possible.

This article was sponsored by Dana Incorporated.

Fleet Equipment Magazine