The CV joints are a key component of your Audi A4's suspension and drivetrain. Even on the all-wheel drive A4, If a CV joint fails, it's the equivalent of having an entire axle fail, as the CV joint at the outer end is what helps drive power to the wheels. CV joints typically need to be replaced if you notice a clicking noise when you are turning the wheel. The common cause of failure is grease loss from the joint, which is usually caused by an aged rubber CV boot, which sits over the joint.
Remove any centre-caps that may be on your wheels and remove the large bolt in the centre, using your 23-mm socket wrench or 14-mm Allen wrench. The size will differ depending on the model year of your A4.
Loosen, but do not remove, the lug nuts on both of your front wheels.
Position the floor jack beneath each jack point, which are located behind the front wheels on each side, and raise both front corners of the car, one at a time. Once you have one corner raised, position a jack stand underneath it to support the car, then repeat on the other side.
Remove the lug nuts that secure your front wheels and then remove both front wheels.
Follow the axle from the wheel-end to where it connects to the differential, underneath your car near the centre. Remove each of the six securing bolts by using your 8-mm triple square hex wrench.
Disconnect the ABS sensor that is connected to your wheel hub's housing.
Using your 16-mm open wrench and 16-mm socket wrench, remove the long bolt that connects the axle to your upper control arms.
Gently tap at the bottom of the upper control arms with your hand until they part.
Turn your steering wheel all the way to the left to make room for the axle to come out.
Pull the axle directly out of place and place it in between the large vice. Remove any remnant rubber CV boot material and pull off the CV joint from the axle.
Slide the new CV boot over the axle, then pack the new CV joint full of the high temperature grease.
Slide the new CV joint on to the axle and into the rubber CV boot.
Tighten the circular metal clam that goes around the boot to secure it to the joint.
Reinstall the axle by first sliding it into the wheel hub and then aligning the rubber-booted end with the differential at the centre of the car.
Reinstall the six securing bolts around the axle using your 8-mm triple-square hex wrench.
Reconnect the axle to your upper control arms using your 16-mm open wrench and socket wrench, ensuring that the bolt is torqued to 30ft-lb.
Re-install the front wheels and insert the lug nuts, but do not tighten them all of the way.
Using the floor jack, lower each front corner of your A4 and remove the jack stands.
Reinstall the bolt that goes into the centre of the wheel using your 23-mm socket wrench or 14-mm socket wrench and ensure it is torqued to 85ft-lb. Tighten the lug nuts on your front wheels to complete the installation.