Universal joints allow drive shafts to move up and down with the suspension while the shaft can be moving so power could be transmitted when the travel shaft isn’t in a right line between the transmission and drive wheels.
Rear-wheel-drive vehicles own universal joints (or U-joints) at both ends of the travel shaft. U-joints connect to yokes that also allow drive shafts to go fore and aft as automobiles review bumps or dips in the street, which successfully shortens or lengthens the shaft.
Front-drive vehicles also U Joint china employ two joints, called regular velocity (or CV) joints, nevertheless they are a several kind that also compensate for steering changes.
On rear-drive vehicles, one signal of a donned U-join is a “clank” sound when a drive gear is engaged. On front-drive cars, CV joints generally make a clicking noises when they’re put on. CV joints are included in protective rubber boots, and if the boot footwear crack or are or else damaged, the CV joints will eventually lose their lubrication and be ruined by dirt and moisture.
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 teach some flexibility. That is needed as all vehicles flex while in motion.
U-joints are located on each of the ends of the rear travel shaft, whereas CV-joints are found on front wheel travel vehicles. Each allows the drive shaft to rotate as the differential movements in relation to the rest of drive train attached on the chassis.
The U-joint functions to save wear and tear on your own vehicle’s transmission. Failure to get a universal joint replacement done when required can lead to substantial 
damage to your vehicle in the future.
There are some warning signs that U-joint or CV-joint is failing. They incorporate: