The drop arm (also called Pitman arm) is rigidly connected to the cross-shaft of the steering gear at its upper end, while its lower end is connected to the link rod arm through a ball joint.
Stub axle is rigidly attached to the other end of link rod arm. Each stub axle is has a forged track rod arm rigidly bolted to the wheel axis. The other end of track rod arms is connected to track rod by means of ball joints.
In case of conventional rigid axle suspension, the main axle beam ensures the movement of stub axle in the horizontal plane only, there is no vertical deflection of the suspension and hence there is no change in the effective track-rod length.
In case of Independent suspension, the two stub axles can move up or down independent of each other due to which distance between ball-joint ends of the two track rod arms is continuously varying. Here three piece track rod is used , the centre portion being called relay rod is used , which is connected at one end to the idler arm supported on body structure and to drop arm of steering gear at the other end through ball joints