Universal joints allow travel shafts to move along with the suspension as the shaft can be moving so power can be transmitted when the drive shaft isn’t in a straight line between your transmission and travel wheels.
Rear-wheel-drive vehicles have universal joints (or U-joints) at both ends of the drive shaft. U-joints hook up to yokes that likewise allow travel shafts to go fore and aft as automobiles go over bumps or dips in the street, which U Joint efficiently shortens or lengthens the shaft.
Front-drive vehicles also employ 
two joints, called constant velocity (or CV) joints, however they are a different kind that also compensate for steering improvements.
On rear-drive vehicles, one sign of a worn U-join is a “clank” sound whenever a drive gear is involved. On front-drive automobiles, CV joints generally make a clicking noise when they’re donned. CV joints are covered by protective rubber boots, and if the boot footwear crack or are or else ruined, the CV joints will lose their lubrication and be harmed by dirt and wetness.
A U-joint is found in both front wheel travel and rear wheel travel cars. Although they are different in design, they possess the same purpose of giving the drive coach some flexibility. This is needed as all cars and trucks flex while in motion.
U-joints are located on each of the ends of the trunk drive shaft, whereas CV-joints are found on front wheel travel vehicles. Each allows the travel shaft to rotate as the differential techniques in relation to the others of drive train attached on the chassis.
The U-joint functions to save lots of wear and tear on your vehicle’s transmission. Failure to have a universal joint replacement done when necessary can result in substantial damage to your vehicle in the future.
There are some indicators that U-joint or CV-joint is failing. They incorporate: