Universal joints allow drive shafts to move along with the suspension as the shaft is moving so power could be transmitted when the drive shaft isn’t in a right line between your transmission and travel wheels.
Rear-wheel-drive vehicles have universal joints (or U-joints) at both ends of the travel shaft. U-joints connect to yokes that likewise allow travel shafts to go fore and aft as vehicles review bumps or dips in the road, which successfully shortens or lengthens the shaft.
Front-drive vehicles also use two joints, called frequent velocity (or CV) joints, but they are a several kind that also compensate for steering alterations.
On rear-travel vehicles, one sign of a put on U-join is a “clank” sound when a drive gear is involved. On front-drive cars, CV joints frequently make a clicking sound when they’re put 
on. CV joints are included in protective U Joint rubber boot footwear, and if the boot footwear crack or are normally ruined, the CV joints will lose their lubrication and become destroyed by dirt and wetness.
A U-joint is situated in both front wheel drive and rear wheel drive cars. Although they are different in design, they have the same purpose of giving the drive coach some flexibility. That is needed as all vehicles flex while in action.
U-joints are located on each one of the ends of the trunk drive shaft, whereas CV-joints are found on front wheel drive cars. Each allows the travel 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 lots of wear and tear on your own vehicle’s transmission. Failure to get a universal joint substitute done when necessary can result in substantial damage to your car in the future.
There are some indicators that U-joint or CV-joint is failing. They involve: