How a Car CV Axle Joint Works

A CV joint or constant velocity joint is a type of mechanism that connects two  fixed rotating shafts. This joint allows the shafts to be connected while axis pivots  change, for example when suspension or steering operation occurs. CV joints are  widely used in front-wheel and rear wheel drive cars CV joints can deliver torque  more evenly then conventional "U" joints.  The CV joint is used because of its ability to transmit more even torque throughout  a particular flex range. A CV joint can also deliver power on a wider range of angles  then "U" joints, which makes them more desirable than its older counterpart. One  difference between the two joints is the way they are serviced. A CV joint is constructed  with a rubber boot that is meant to contain the lubricating grease. A typical "U"  joint has grease seals on each bearing cap so a boot is not needed.  The CV  joint is virtually non-serviceable unless the boot ruptures or extreme conditions  exist, like high mileage or abuse. When the CV joint fails simply replace it with  a new unit. A "U" joint is much like the CV joint in that it too doesn't require  service unless fitted with a zirk fitting meant to allow grease to be inserted.

There are other types of flexible couplings such as a Thomas or Oldham joint.  These joints use a rubber fiber flex material and are mainly used for drivelines  and not axle shaft joints. When replacing a CV joint you made need to replace the  axle assembly depending on the design of the car. Some manufactures allow the joint  to be replaced separately; you will need to check with a part supplier to inform  you on which type your car has. A CV joint consists of a six steel balls that run  in grooves on a spherical ball and socket which are held in place by a cage between  the ball and socket. The cage always floats in a neutral position holding the balls  in the correct location. While the joint is in motion the individual balls move  back and forth along the grooves.

Common Problems
•Front wheel drive cars utilize front drive axles with CV (constant velocity) joints. When CV joints start to wear they will bind up on acceleration, especially in a turn. This causes a vibration or a clicking noise in the front suspension that can transfer to the vehicle. To check for this condition. Remove drive axles and inspect flexibility of each CV joint. If a bind or hard spot is observed the CV Joint/Axle needs to be replaced.
•A CV joint utilizes a grease boot that supplies grease for lubrication for the joint. When this boot fails it can fling grease to the inner fender well and the back side of the tire. To repair this condition the CV axle must be removed. Some CV boot replacement kits or what they call a "spilt boot". These boot look desirable because the ease of replacement. But most of these applications leak and require replacement prematurely.

To remove and replace a CV boot or axle you must disconnect the lower control  arm from the spindle. Then remove the corresponding inner and outer nuts and bolts.  Some drive axles are held in by a snap ring and all that is needed to remove them  is a large wedge or pry bar to leverage the axle from the transmission or differential.

•Front wheel drive cars utilize front drive axles with CV (constant velocity) joints. When CV joints start to wear they will bind up on acceleration, especially in a turn. This causes a vibration or a clicking noise in the front suspension that can transfer to the vehicle. To check for this condition. Remove drive axles and inspect flexibility of each CV joint. If a bind or hard spot is observed the CV Joint/Axle needs to be replaced.

•A CV joint utilizes a grease boot that supplies grease for lubrication for the joint. When this boot fails it can fling grease to the inner fender well and the back side of the tire. To repair this condition the CV axle must be removed. Some CV boot replacement kits or what they call a "spilt boot". These boot look desirable because the ease of replacement. But most of these applications leak and require replacement prematurely

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