ODM TO-8-8521 CV Axle Shaft CV axles are a modern drivetrain component commonly found on all front wheel drive vehicles. They serve the purpose of transferring the power from the vehicles transmission and differential to the wheels so that they can propel the vehicle forward. They have a greased flexible joint that allows the axle to flex according to the road conditions The joint is lubricated with grease and covered in a rubber boot to protect it from dirt and debris. Because the CV axles are the direct link that transfers the power of the engine to the wheels, they are subject to high amounts of stress over time and will eventually wear out and require replacement. When they do wear out,CV axles usually will produce a few symptoms that can alert the driver that they require attention One of the most common and most noticeable symptoms of a bad or failing CV axle shaft assembly is an audible clicking noise when turning. When CV axles become excessively worn, the joints will become loose and click when turning. The clicks may become louder or more pronounced during sharper and faster turns, and will be heard on the side with the faulty CV shaft Another symptom of a problem with the CV axle shafts is grease on the insde edge of the tireor along the undersides of the vehicle. This is usually caused by a torn boot leaking grease, and it being tossed around while the axle turns. A leaky boot will eventually lead to CV joint failure, as dirt and debris will get into the boot and damage the joint If a CV joint or axle shaft is damaged in any way that affects its balance while rotating, it will cause the shaft to vibrate excessively while operating the vehicle. The vibrations may oscillate in speed, or become more pronounced as vehicle speed increases. Excessively vibrating CV shafts can interfere with the handling and ride characteristics, and to the overall safety and comfort of the vehicle. Usually the CV axle will need to be replaced if it is damaged enough to cause vibrations