Front wheel drive axles have constant velocity joints or CV joints located on the inboard and outboard ends. These joints allow for movement as the wheel is turned and as the vehicle travels over bumps in the road. As the joint wears or loses vital lubrication it starts to become noisy. The most common problem is the rubber boot that protects the joint wears, breaks open and loses its lubrication. If the joint is still good, boot kits are available to replace the boot and lubrication.
It's important to listen to the customer and road test the vehicle before performing a visual inspection. Find if out if the noise occurs while accelerating or while turning. During the road test listen for familiar noises like worn wheel bearings that produce a growling sound that increases with vehicle speed.
Inboard joint: A worn or faulty inboard joint makes its most noise while accelerating and decelerating. This is often due to a lack of lubrication in the tripod bearings that must slide smoothly in and out of the encasing. They will also make a vibration around 40-50 mph similar to an out of balance tire. Most of these joints can be serviced by removing the snap ring from the end of the axle shaft and tapping on the tripod case with a soft hammer.
Outboard CV-joint: A worn or faulty outboard CV-joint makes its most noise while cornering. This is even more noticeable in reverse. Always use caution and pay attention while road testing a vehicle and don't get so engrossed in diagnosis that you cause an accident.
While traveling forward turn the wheel left and right while listen for a clicking noise. A faulty joint will make its most noise when it is on the inside of the turn. These joints can make a squeaky noise while traveling in a straight line, but will make the most while turning. They consist of large ball bearings incased in a cage that allows the joint to rotate in circles as the wheel is turned.