system must perform several important functions,
pitman arm normally uses a ball-and-socket joint to
which are as follows:
connect to the center link.
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 operators hands.
Absorb most of the shock going to the steering
wheel, as the tires hit bumps and holes in the
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.
Allow for suspension action.
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.
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.
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
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.