Servicing the Constant Velocity (CV) joints is a maintenance task that should be performed at least every 50,000 miles or so. Why? Because the grease in the CV joints will harden and lose its lubricating properties over time. This will lead to premature failure of the joint. A properly maintained joint will easily outlast most street-driven vehicles. While not too terribly difficult, it is a messy and time consuming task.
On each end of the shaft is a ribbed rubber boot that covers a constant velocity joint (CV joint). The CV joint is the flexible coupling that allows the outer wheel to steer, and the shaft to follow the up and down motions of the suspension as the vehicle travels down the road.
The outboard CV joint (the one that connects to the drive wheel) typically has a much wider operating angle than the inboard CV joint that connects to the transaxle. This is because the outer joint may have to turn up to 50 degrees off center when the front wheels are steered. The inboard joint, by comparison, rarely sees an operating angle of more than about 20 degrees. Consequently, different types of joint designs may be used for the inner and outer joints.
Outboard joints that do not plunge in and out are called "fixed" joints.
JOINT LUBRICATION
CV joints require a special type of high temperature, high pressure grease. Ordinary chassis grease or multipurpose grease should never be used in a CV joint.
The condition of the grease as well as the amount of grease in the joint will determine how long the joint lasts. One of the purposes of the boot that surrounds the CV joint is to keep dirt and moisture out. The other is to keep the grease in. If a boot is torn, cracked, punctured or comes loose, dirt and water can contaminate the grease in the joint causing accelerated wear which will eventually lead to joint failure. Loss of grease can also occur which will further shorten the life of the joint. So the boots must be in good condition to protect the joint.
Boots often become brittle with age and exposure to heat. Boots can also be damaged by road hazards and the careless use of j-hooks by a tow truck operator. Old boots should never be reused if a CV joint is being replaced. That’s why most new CV joints come with a new boot.
