A Chevrolet control arm is the suspension component that is sometimes referred to as an A-arm or wishbone on some models. The control arm provides for a solid connection from the hub of the wheel to the frame in the front suspension of your vehicle.
The introduction of this new shaped part for connecting the wheel to the car was necessary since the use of the MacPherson strut began to be used as part of the independent front suspension on many of the new Chevrolet models.
The Chevrolet control arm can be seen by looking at the bottom of the strut. This is the connection point on the hub for it. It is the bar that is also connected to the frame. It could be straight or in the shape of an L. The only purpose of the control arm on your Chevrolet is to minimize the movement of the wheel forwards and backwards while allowing it to travel up and down.
If you Chevrolet is of the old style the control arm will be in the shape of an A and there is an upper and lower. The largest difference between these two types of suspensions in the amount of play forwards and backwards. The A-frame style allows for 2% play while the one used with the MacPherson Strut only permits 1% of play.
No matter the design, the control arm will likely last the life time of your vehicle. The parts that will need to be changed, however, are the ball joint where it is joined to the spindle and wheel hub or the bushings where it mounts to the frame. These are pressed into place and are the reason the entire component has to be replaced.