In some applications, tight clearances would make it nearly impossible to gain access to a Zerk fitting. Premature failures, like those of the first-generation Chevy Trailblazer or Ford Transit Connect, contribute to a negative perception of the sealed joint design. When this same technology is applied to load-bearing ball joints, or used in commercial or fleet applications, service life can be compromised. This design is adequate for many automobiles and some light trucks, especially when designing components like sway bar links and tie rod ends. A highly polished steel ball stud rotates within an injection-molded polymer socket, resulting in a low-friction joint capable of smooth articulation under moderate loads. The sealed joint relies heavily on polymer (plastic) technology, decreasing raw material costs when compared to metal-on-metal designs. Material costs make sealed-for-life suspension components an attractive option for OEM engineers, as well as the folks in their accounting offices.
We aren’t seeing the vehicles as often, so more can go wrong between visits. This may be a contributing factor in our perception that we see more outright failures of components. As the average OCI increases and these other services need to be performed less frequently, our opportunity for periodic inspection declines. For the OEMs, extended service intervals translate into a reduction in periodic maintenance costs, as well as the appearance of reliability and longevity. Mileage-based service recommendations are often multiples of the OCI, providing vehicle owners (and service technicians) with a convenient and logical maintenance schedule. For years, the oil change interval (OCI) has been a basic reference point for many other maintenance services, including chassis lubrication. The grease fitting is going the way of the 3,000-mile oil change interval, and for many of the same reasons.