With proper service, CV joints can have a long life, despite having to perform extremely difficult jobs in hostile environments. They must endure extreme heat and cold and survive the shock of hitting pot holes at high speeds. Fortunately, high torque loads during low-speed turns and many thousands of high-speed miles normally do not bother the CV joint. It is relatively trouble-free unless damage to the boot or joint goes unnoticed.

All CV joints are encased in a protective rubber (neoprene, natural or silicone) or thermoplastic (Hycrel) boot. The job of the boot is to retain grease and keep dirt and water out. The boots also pump grease through the joint as they flex with the movement of the suspension. The importance of the boot cannot be overemphasized, because without its protection, the joint does not survive. For all practical with grease and installed, it requires no further maintenance. A loose or missing boot clamp, a slit, tear, or even a small puncture in the boot itself, allows grease to leak out and water or dirt to enter. Consequently, the joint is destroyed.

Outer joints in front-wheel-drive vehicles tend to wear somewhat faster than inner joints die to the added motions of steering. By the time the outer joint produces noticeable wear symptoms, the inner joint might be on the verge of needing replacement. The decision as to whether to replace both joints when the half shaft is removed depends on the circumstances. If the vehicle has low miles and joint failure is the result of a defective boot, there is no reason to replace both joints. On a high-mileage vehicle where the bad joint has actually just worn itself out, it might be wise to save the expense and inconvenience of having the half shaft removed twice for CV joint replacement.

CV joints failure is usually preceded by various noticeable symptoms. If these signs are ignored, the results of complete failure could be very serious. For example, if an outer joint seizes due to loss of lubricant, it cause loss of steering control. If the joint breaks, the half shaft or axle shaft could drop out of the car. Because of these possibilities, any symptom of a potential CV joint problem could be properly investigated and the appropriate service performed.

CUSTOMER CARE

There has been some confusion about towing a front-wheel-drive vehicle. It is correct for you to advise your customer that CV joints require only one special towing precaution. If a front-wheel-drive car requires towing, tell your customer to be sure that the tow-truck operator does not use J-hooks on the half shaft or lower control arms. The hooks can bend the half shafts or slide along the shafts or arms and rip the boots. Position the hooks on the subframe or cross member only. In fact, it is a good idea to point out these surfaces to your customer.