Universal joints allow drive shafts to move along with the suspension while the shaft can be moving so power could be transmitted when the drive shaft isn’t in a straight line between your transmission and drive wheels.
Rear-wheel-drive vehicles include universal joints (or U-joints) at both ends of the travel shaft. U-joints connect to yokes that as well allow drive shafts to go fore and aft as automobiles review bumps or dips in the street, which effectively shortens or lengthens the shaft.
Front-drive vehicles also work with two joints, called regular velocity (or CV) joints, but they are a different kind that also compensate for steering improvements.
On rear-travel vehicles, one indication of a donned U-join is a “clank” sound when a drive equipment is engaged. On front-drive cars, CV joints generally make a clicking sound when they’re donned. CV joints are covered by protective rubber shoes or boots, and if the footwear crack or are or else broken, the CV joints will lose their lubrication and be damaged by dirt and wetness.
A U-joint is found in both front wheel travel and rear wheel drive cars. Although they will vary in design, they have the same purpose of giving the drive teach some flexibility. This is U Joint necessary as all cars and trucks flex while in action.
U-joints are located on each one of the ends of the trunk drive shaft, whereas CV-joints are located on front wheel drive automobiles. Each allows the drive shaft to rotate as the differential moves in relation to the others of drive train 
attached on the chassis.
The U-joint functions to save wear and tear on your vehicle’s transmission. Inability to have a universal joint substitute done when required can result in substantial damage to your vehicle in the future.
There are several warning signs that U-joint or CV-joint is failing. They contain: