Universal joints allow travel shafts to move up and down with the suspension while the shaft is usually U Joint moving so power can be transmitted when the drive shaft isn’t in a straight line between the transmission and drive wheels.
Rear-wheel-drive vehicles currently have universal joints (or U-joints) at both ends of the travel shaft. U-joints hook up to yokes that as well allow travel shafts to go fore and aft as automobiles review bumps or dips in the road, which successfully shortens or lengthens the shaft.
Front-drive vehicles also make use of two joints, called continuous velocity (or CV) joints, however they are a different kind that also compensate for steering changes.
On rear-drive vehicles, one signal of a donned U-join is a “clank” sound whenever a drive equipment is involved. On front-drive cars, CV joints typically make a clicking noises when they’re 
worn. CV joints are included in protective rubber boot styles, and if the shoes or boots crack or are usually harmed, the CV joints will eventually lose their lubrication and be ruined by dirt and dampness.
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 reason for giving the drive train some flexibility. This is necessary as all vehicles flex while in action.
U-joints are located on each of the ends of the rear drive shaft, whereas CV-joints are located on front wheel drive vehicles. 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 get a universal joint substitute done when required can bring about substantial harm to your car in the future.
Here are a few indicators that U-joint or CV-joint is failing. They involve: