In recent years, manufacturers of heavy vehicles such as tractor-trailer trucks, large recreational vehicles and buses have implemented recalls because of excessive wear and failure of the steering knuckle king pin, a component of the front wheel steering mechanism, resulting in accidents. Freightliner, one such manufacturer, has recalled some of its products. Drivers and technicians should be alert to the symptoms of these problems.
While the engine is running, but with the vehicle standing still, a driver or technician inside the vehicle should rotate the steering wheel from side to side (lock to lock.) An observer outside the vehicle should indicate how much the wheels appear to move. If there appears to be loss of motion or too much motion without the wheels moving, there may be a problem with the steering mechanism, including the knuckle king pin.
While the vehicle is being driven, the driver or technician may observe other indications of steering mechanism problems. If it is difficult to keep the vehicle pointed in the proper direction, or if it tends to pull to one side or the other, this is an indication of serious problems. The front wheels may “shimmy,” causing the steering wheel to vibrate excessively. The steering wheel may not return to its proper start position after a turn. There also may be too much “play” in the steering wheel or too much steering wheel movement without corresponding movement of the vehicle’s front wheels.
A trained and experienced technician can hear the presence of sounds that may indicate multiple problems in the suspension and steering system. These sounds can include grinding, hissing, squealing or harmonic overtones. These sounds may be observable either while the vehicle is at rest or being driven.
The technician should take measurements with specially designed tools and compare the resulting measurement with the manufacturer’s suspension and steering specifications. If the results fall outside of the manufacturer’s suggested tolerances, there may be a problem with the mechanisms.
