There is a pair of Toyota CV axle shafts on all front wheel drive vehicles from this Japanese manufacturer. Unlike rear wheel drive vehicles that can have a solid (live) axle, front wheel drive cars must have flexibility since the wheel not only rotates but also turns side to side. The CV axle shaft is connected to the transmission by a CV joint at one end. It is this CV joint that will wear out over time due to the stress and strain that it experiences in transferring the power of the Toyota engine to the wheels when it is creating forward motion of the vehicle. The end of the Toyota CV axle shaft that is connected to the drive train by the CV joint is covered from the factory with a CV boot. This boot is in place to keep grease packed around the joint so it can be heavily lubricated at all times. If this CV boot is ripped or torn for any reason and the grease is permitted to leak out, damage will occur to the CV axle shaft unless the boot is repaired immediately on your Toyota. A visual inspection of the CV axle shaft cannot generally be accomplished or is necessary as long as the CV boot is in place. What a driver can do is be observant in the noises that are created when the Toyota is placed into gear and when it is traveling account a sharp corner. If a knocking noise is heard in either situation, then the CV joint is not longer in a tight configuration and will require the CV axle shaft to be replaced. This generally only occurs when the CV boot has been ripped and the grease is no longer around the CV joint causing it to wear prematurely.