There are two Chevrolet Axle Shafts in the differentials of all rear wheel driven vehicle from this manufacture. The axle shafts have a set of spines on one end and the other is fitted through the rear brake plate. This is the end with the wheel studs on it that the wheels are mounted too on your Chevrolet.
The Chevrolet axle shafts are made of solid cold roll steel that very rarely need to be replaced unless they are bent from a collision with an extremely hard object. If the rear gear oil in the differential is also not changed regularly, the end of the axle shafts can also be damaged requiring them to be in need of replacement. This changing of the differential gear oil should be on the Chevrolet owner's periodic maintenance schedule.
The replacement of the axle shaft requires the rear differential backing plate to be removed and the pins holding the shaft in place on the spider gears removed. Then the axle can be pulled out of the differential housing unit. Before the new axle shaft is put into place the wheel bearing in the housing unit should be pulled and inspected. To expose this bearing, the seal in the brake plate will have to be removed. If the axle is being replaced, so should the bearing and seal just to make sure the axle will be able to perform it duty as expected by the owner of the vehicle.
Once the new axle is in place and the pin is reinserted into it holding the axle in the spider gears, new gear oil should be used to fill the differential on your Chevrolet. Remember this oil not only lubricated the axle and differential but also the axle wheel bearing.