Driving Home a Point
After-market auto parts may be unreliable, unsafe A beautiful, 1966 big-block Corvette is accelerating down the highway when, without warning, the rear axle shaft separates, causing the suspension to tip. The tire pounds its way through the fiberglass wheel well, causing the car to fishtail. The car spins repeatedly – finally coming to a stop with a severely damaged body and a completely stunned driver.
What happened? Forensic investigation concluded that a universal joint in the rear half shaft failed catastrophically. While this Corvette’s original universal joints were designed without lubrication holes, after-market u-joints had been installed that were cross-drilled. This weakened the joints so they were unable to handle the added loads of suspending the vehicle. The car’s remaining suspension components fell outward, the tire destroyed the rear wheel well, and the car lost control.
While original equipment manufacturers (OEMs) have component designs that can and do fail, for the most part they are safer than after-market products. After-market parts producers don’t always maintain design integrity with their components. Many after-market universal joints have nowhere near the life expectancy or durability of OEM parts. Seal and other component failures can cause seized and damaged joints – even allowing the drive shaft to drop out of the car! Cheap, inferior knockoffs of other replacement parts also abound. Some after-market suppliers copy planetary gear sets and pump rotors in dimensions that are not reflective of strength and durability requirements – with potentially disastrous consequences. Poor-quality pump seals, for example, can completely fail, or result in a vehicle fire, in just a few thousand miles of use.
In their exhaust system components, a number of after-market companies use mild-steel, single-wall pipe. Especially in the typical northern environment, these have a much shorter life expectancy than OEM-specified pipe, corroding more easily and potentially exposing passengers to deadly carbon monoxide.
Inferior chassis parts can present another problem. Some after-market ball joints are sold separately – not already press-fit into the lower control arm – with the customer responsible for installation. These joints don’t always fit properly, however, which can lead to control-arm breakage.
In all of these cases and more, metallurgy, testing and automotive engineering experts can determine if an inferior automotive component has caused or will cause a vehicle liability problem.
-Jeff Wingfield, Mechanical Engineer