Universal joints allow drive shafts to move along with the suspension as the shaft is usually moving so power could be transmitted when the travel shaft isn’t in a directly line between your transmission and drive wheels.
Rear-wheel-drive vehicles have got universal joints (or U-joints) at both ends of the travel shaft. U-joints hook up to yokes that likewise allow drive shafts to go fore and aft as automobiles go over bumps or dips in the street, which properly shortens or lengthens the shaft.
Front-drive 
vehicles also make use of two joints, called frequent velocity (or CV) joints, nonetheless they are a distinct kind that also compensate for steering improvements.
On rear-travel vehicles, one indication of a donned U-join is a “clank” sound whenever a drive equipment is engaged. On front-drive cars, CV joints typically make a clicking sound when they’re put on. CV joints are included in protective rubber boot styles, and if the boot styles crack or are or else damaged, the CV joints will eventually lose their lubrication and become damaged by dirt and dampness.
A U-joint is found in both front wheel drive and rear wheel drive cars. Although they are different in design, they possess the same reason for giving the drive teach some flexibility. This is necessary as all vehicles flex while in motion.
U-joints are U Joint located on each of the ends of the trunk drive shaft, whereas CV-joints are located on front wheel drive cars. Each allows the drive shaft to rotate as the differential moves in relation to the rest of drive train installed on the chassis.
The U-joint functions to save wear and tear on your vehicle’s transmission. Inability to possess a universal joint replacement done when required can bring about substantial damage to your car in the future.
There are some warning signs that U-joint or CV-joint is failing. They contain: