Many people find out they've got damaged CV-boots from their mechanic when getting an oil change or other routine maintenance. If the seal that keeps dirt and grime out of CV joints remains breached, the joint may be damaged and cause a grinding noise when turning. If this is happening to you, you'll need a replacement Audi axle assembly. The transfer of rotational force between the wheels and the transmission should be seamless. To accomplish this, the CV-joints must be very carefully greased and packed away from the elements. The rubber gasket forming a seal around the CV-joint is called a boot, and must be tough to withstand the beating many vehicles give them. Some people recommend trying to save a few dollars using old CV or U-joints and replacing the boot alone or even a sealed boot-assembly. This requires you to crack the boot in two with a special tool, flush the old grease out from the boot, repack with just the right amount of grease, and put it all back together without making a mess and making sure everything is secure and tight. Or, you could save yourself the time and trouble by getting the whole Audi axle assembly from car-stuff.com. When you purchase the whole assembly, you will eliminate the possibility of doing all the work reinstalling a damaged joint. No need to fret over making sure the seals are tight: and the price is very comparable after labor is factored in. The lower life expectancy of replaced joints makes purchasing the entire Audi axle assembly a very good deal and a time saver.