CV (constant velocity) joints were first introduced on front-wheel drive vehicles. There are two joints per one CV joint unit; an inner and outer bearing joint. The inner attaches to the splines of the transmission or transaxle while the outer joint attaches to the splines of the wheel hub assembly. CV joints are unserviceable and do not require maintenance. While it's rare for them to fail, because they're exposed to the undercar elements the rubber boots can crack or split. But even after normal wear and tear, the internal bearings can also wear and weaken.
Test drive the vehicle first. For outer CV joint failure, a pronounced clicking or crunching sound will emit when taking turns, which places additional stress on the bearings.
Test drive for inner CV joint failure. Worn splines on the spindle of the inner CV joint can slip inside the transmission or transaxle. When backing up, accelerating and decelerating, listen for pronounced clunking and slipping. While similar symptoms may occur with inner transmission or transaxle wear or worn differential gears, it is most commonly a bad inner CV joint.
Take note while test driving for clunking noises, vibrations or shuddering that increase with the revolution of the tires upon acceleration demand. These symptoms may be indicative of internal joint weakness or failure.
Place a tire block against a tire on the opposite axle of the vehicle from the CV joint you wish to inspect.
Raise the quarter panel of the vehicle (or the entire axle) and then support it onto jack stands. You can apply the parking brake if you're visually inspecting front CV joints, but do not apply it for rear CV joint inspections because it will not allow you to spin the wheels.
Look under the raised wheel(s) and spin the tire. Use a flashlight or shop light to visually inspect the outer and inner CV joint boots for obvious cracks or rips. CV joint boots that have torn completely open will also have grease sprayed out and coating the inner rim of the tire and the wheel knuckle.
Turn the steering wheel all the way to one side and then spin the front wheel(s) to give you a better visual inspection of the front CV joint boots for dry rotting, cracks or rips that are not as obvious.
Place your fingers inside the torn boot of the CV joint (if applicable) and rub the grease between your fingers. If it feels gritty, then it has become contaminated with dirt and other grit from the roads. While the CV joint could possibly be cleaned and repaired, it would have to be removed from the vehicle and the labour charges to recondition the joint may be more than replacing it.
Be sure to look for dry-rotting cracks in the inner portion of the accordion shaped boots. While it may not be indicative of CV joint failure, you can have the boots replaced before the internal bearings of the CV joint become contaminated.
The popularity of CV joints has many vehicle manufacturers now putting them on rear-wheel drive independent suspension vehicles and in all-wheel and four-wheel drive vehicles.