IDLER & PITMAN ARMS
Used in parallelogram steering systems, the idler arm helps maintain proper toe geometry while the wheels are steered by
duplicating the motions of the pitman arm. The pitman arm attaches to the steering box and moves the center link, idler arm
and tie rods to steer the wheels. Some steering systems have two idler arms. They function as hinge points for the steering
linkage as the wheels are steered.
Excessive play in either component can upset toe alignment and cause steering looseness and wander. Pitman arms cause
few problems because they are attached to the steering gear output shaft. But idler arms have a large bushing that often
wears, allowing the arm to wobble as it rotates. This is what causes the loose feeling in the steering and contributes to steering
wander and toe wear on the front tires.
Specifications vary as to how much play in the idler arm is acceptable. Some allow little or no play, while others allow some
movement when the arm is pulled down on with a specified amount of force (typically 25 lbs). If the arm deflects more than the
specified amount (typically 0.125 inches), the idler arm is worn and needs to be replaced. Always refer to the vehicle
manufacturers specifications when checking idler arms.
The idler arm mounting bracket and bolts should also be inspected. If the bracket is cracked, it must be replaced. Loose bolts
can be tightened. Mounting holes should be checked to make sure they are not out of round or worn.
The steering linkage should be centered before replacing the idler arm. Toe alignment should be checked and adjusted if
necessary after replacing the idler arm.