This article explain how an automotive CV joint works. This information pertains
to all front wheel drive and independent suspension vehicles.
A CV joint (constant velocity) joint is a type of multi-ball flex joint that
connects two fixed rotating shafts and is designed to transfer force from the transmission
to the drive tries. Theses joints have a range of motion that is more broad than
conventional U joints
CV Joint Axle and Boot
CV joints are also designed to deliver engine torque evenly throughout their range
of motion were as U joints give isolated movement in extreme angles.
Consisting of a series of hardened metal balls encased within a housing while
using an inner metal cross (center) in which the axle is connected. These joints
can be disassembled and inspected by removing the axle and forcing the inner cross
beyond center. This will allow the balls to be removed and reassembled. Once serviced
a graphite based grease is needed to properly lubricate the joint. A rubber boot
is used to prevent grease from being thrown out of the joint while in operation.
Once a boot has failed it should be repaired to prevent failure and a more
Service on this style of joint is minimal for the exception of a visual inspection
the joint will continue to operate until failure. The first signs of failure include
clicking while turning under power and vibration under acceleration. The
CV axle must be removed
and inspect by checking the range of motion and looking for any rough spots in the
motion. Some manufacturers design the joint to be replaced as a full axle only.
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. These joints gave out under pressure which warranted
the inventions of the CV and U joint. There is no known inventor of these joints.
- CV joints fail causing acceleration bind up.
- CV boot fail allowing grease to leak out warranting replacement.
Article first published 2016-02-04