system must perform several important functions, which are as follows:

Provide precise control of front-wheel direction.

Maintain the correct amount of effort needed to turn the front wheels.

Transmit road feel (slight steering wheel pull caused by road surface) to the operator's hands.

Absorb most of the shock going to the steering wheel, as the tires hit bumps and holes in the road.

Allow for suspension action.

STEERING LINKAGE

Steering linkage is a series or arms, rods, and ball sockets that connect the steering mechanism to the steering knuckles. The steering linkage used with most manual and power steering mechanisms typically includes a pitman arm, center link, idler arm, and two tie-rod assemblies. This configuration of linkage is known as parallelogram steering linkage (fig. 8-19) and is used on many passenger vehicles.

Pitman Arm

The pitman arm transfers steering mechanism motion to the steering linkage (fig. 8-19). The pitman arm is splined to the steering mechanisms output shaft (pitman arm shaft). A large nut and lock washer secure the pitman arm to the output shaft. The outer end of the pitman arm normally uses a ball-and-socket joint to connect to the center link.

Center Link

The parallelogram steering linkage (fig. 8-19) uses a center link, otherwise known as an intermediate rod, track rod, or relay rod, which is simply a steel bar that connects the steering arms (pitman arm, tie-rod ends, and idler arm) together. The turning action of the steering mechanism is transmitted to the center link through the pitman arm.

Idler Arm

The center link is hinged on the opposite end of the pitman arm by means of an idler arm (fig. 8-19). The idler arm supports the free end of the center link and allows it to move left and right with ease. The idler arm bolts to the frame or subframe.

Ball Sockets

Ball sockets (fig. 8-19) are like small ball joints; they provide for motion in all directions between two connected components. Ball sockets are needed so the steering linkage is NOT damaged or bent when the wheels turn or move up and down over rough roads. Ball sockets are filled with grease to reduce friction and wear. Some have a grease fitting that allows chassis grease to be inserted with a grease gun. Others are sealed by the manufacturer and cannot be serviced.

Figure 8-19. - Parallelogram steering linkage.