4.3 Steering Linkage and Gear Inspection

4.3 Steering Linkage and Gear Inspection

Rack and Pinion Steering Gear Diagnostics

The rack and pinion steering gear converts the rotational movement of the steering wheel into the linear, side-to-side movement needed to steer the wheels. A pinion gear, attached to the steering shaft, meshes with a flat, gear-toothed rack. Rotating the pinion slides the rack left or right.

During inspection, the technician must check for mechanical, mounting, and hydraulic integrity:

• Mounting Bushings: The rack housing is secured to the subframe using rubber mounting bushings. Over time, oil leaks or age degrade the rubber, making it soft or split. This allows the steering gear housing to slide side-to-side when the steering wheel is turned, a condition called "racking." This causes a loose steering feel, delayed response, and an off-center steering wheel. Inspect by watching the steering gear while an assistant turns the steering wheel back and forth under load. Any visible side-to-side movement of the housing indicates failed bushings.
• Hydraulic Leaks: In hydraulic power-assist systems, fluid leaks can occur at three key locations: the input shaft seal (where the steering column connects), the line fittings, and the internal end seals. End seal leaks allow power steering fluid to escape into the steering gear bellows boots.

Outer and Inner Tie Rod Inspection

The steering rack transmits its movement to the steering knuckles via inner and outer tie rod ends. These are ball-and-socket joints that must be inspected for play.

The 9 and 3 O'clock Shake Test

To perform this inspection, raise the vehicle on a hoist:

1. Grasp the tire at the 9 o'clock (front) and 3 o'clock (rear) positions.
2. Push and pull the tire in an alternating, rapid motion to check for steering linkage play.
3. If movement is felt, look at the outer tie rod end. If the ball stud moves inside the housing, or if the boot is torn and discharging grease, replace it.
4. If the outer joint is tight but play is still felt, grasp the inner tie rod through the rubber bellows boot. If you feel the inner rod assembly sliding axially inside the boot before the rack moves, the inner tie rod joint is worn and must be replaced.

Compare this to the 12 and 6 o'clock test, which is used to diagnose wheel bearings and suspension ball joints. Play felt only at 9 and 3 o'clock points directly to steering linkage wear.

graph LR
    A["Steering Wheel"] --> B["Steering Column/Shaft"]
    B --> C["Steering U-Joint"]
    C --> D["Pinion Gear"]
    D --> E["Steering Rack"]
    E --> F["Inner Tie Rod (Under Boot)"]
    F --> G["Outer Tie Rod"]
    G --> H["Steering Knuckle"]

Bellows Boots and Internal Rack Seals

The steering gear bellows boots (dust boots) protect the inner rack shafts and inner tie rod joints from dirt, water, and debris. If a boot is cracked, torn, or has missing clamps, it must be replaced immediately to prevent contamination from scoring the polished rack shaft and damaging the internal seals.

During inspection, the technician should squeeze the bellows boots. The boots should contain only air and a small amount of grease for the inner joint. If a boot is swollen or drips fluid when squeezed, or if fluid runs out when the boot clamp is released, the steering gear's internal hydraulic end seals have failed. Hydraulic pressure is bypassing the seals and filling the boot. Replacing the boot will not fix this; the entire steering gear assembly must be replaced.

Steering Shaft U-Joints

The steering column connects the steering wheel to the steering gear pinion shaft. Because the column cannot run in a straight line due to engine bay components, it uses universal joints (U-joints).

Over time, these U-joints are exposed to road splash, causing them to rust and bind. Symptoms of a binding steering shaft U-joint include:

1. Stiff Spots: The steering wheel feels stiff or hard to turn at specific points, typically binding every 90 degrees of rotation as the joint pivots.
2. Poor Returnability: The steering wheel does not return to center after a turn.
3. Noise: Squeaking or clunking sounds from the dashboard or footwell area during turns. To diagnose, spray the U-joint with penetrant. If the steering effort temporarily decreases, the joint is binding and must be replaced.

Electric Power Steering (EPS) Inspection

Many modern vehicles utilize Electric Power Steering (EPS) instead of hydraulic systems. In EPS designs, an electric motor provides assist torque, which can be located on the steering column, the pinion shaft, or directly on the steering rack housing. When inspecting an EPS system, the technician checks for secure electrical connections and wiring harness routing, ensuring no wires are pinched or rubbed by moving suspension components. While there are no hydraulic lines or fluids to leak, the mechanical components—including the steering gear mounting bushings, inner and outer tie rod ends, and bellows boots—remain the same and require the same physical play inspections as hydraulic systems. Any binding or noise from the electric motor indicates internal gear or motor failure.