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How
Does it Work /
CV Joint
How a CV (Constant Velocity) Joint Works
Introduction:
A CV joint or constant velocity 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.
Typical CV Joint Configuration
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.
Front Wheel Drive Axle
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. For exact
removal instructions consult a
car
repair manual.
How Does it Work /
CV Joint
Check Manufacturer Specific CV joint
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