Steering Gears: Adjustments, Replacement, and Maintenance

1. What are Steering Gears in a Car or Truck?

The steering gear, often called a steering box or steering rack, is the component responsible for converting the rotational motion of the steering wheel into the linear or angular motion required to turn the vehicle's road wheels. Essentially, it is a gear reduction system that multiplies the driver's effort, allowing a heavy vehicle or one with wide tires to be steered with manageable force.

This mechanism is attached to the steering column at one end and to the steering linkage (tie rods and pitman arm, or directly to the knuckles) at the other, bridging the gap between driver control and wheel direction.

2. Different Kinds of Steering Gears and Their Advantages

There are two primary types of steering gears used in modern and older vehicles:

Rack-and-Pinion Gear

**Mechanism:** The steering shaft turns a pinion gear, which is meshed with a long, horizontal toothed bar called the rack. As the pinion turns, the rack moves left or right, directly moving the tie rods attached to the steering knuckles.

• Advantages for Cars and Light Trucks:
• **Simplicity & Light Weight:** Fewer components mean a lighter system.
• **Precise Feedback:** Provides the driver with excellent road feel and control.
• **Better Efficiency:** Fewer friction points lead to greater mechanical efficiency.
• **Compactness:** Easy to package in modern engine compartments.

Recirculating Ball Gear (Steering Box)

**Mechanism:** The steering shaft rotates a worm gear within the steering box. Ball bearings circulate within the gear to minimize friction. This motion moves a ball nut, which in turn engages a sector gear attached to the pitman arm.

• Advantages for Trucks and Heavy Vehicles:
• **High Mechanical Advantage:** Better suited for heavy loads and off-road applications where higher steering forces are required.
• **Durability:** Robust design can withstand harsh conditions and large tires.
• **Less Impact Shock:** Provides greater isolation from road shocks and impacts.

3. How Does a Steering Gear Work in a Car or Truck?

The core principle of any steering gear is leverage and ratio adjustment.

• **Input Conversion:** The steering wheel rotation is the input motion.
• **Gear Reduction:** Inside the gear, the ratio between the input rotation and the output movement (rack slide or pitman arm swing) is fixed to reduce the effort needed by the driver. For example, a common ratio might be 16:1, meaning the steering wheel must turn 16 degrees for the output shaft to turn 1 degree.
• **Output Transmission:** The gear's final output (the movement of the rack or the swing of the pitman arm) is transmitted through the steering linkage (tie rods) to the steering knuckles, causing the wheels to pivot and the vehicle to turn.
• **Self-Locking Feature:** Steering gears are designed to be "irreversible" to a degree, meaning road forces and bumps are heavily dampened and generally do not feed back strongly enough to spin the steering wheel wildly.

4. How to Diagnose a Problem with Steering Gears

Steering gear problems usually manifest as noticeable changes in steering feel or noise. Diagnosis requires careful inspection:

Common Symptoms to Check:

• **Excessive Steering Play (Slack):** If the steering wheel can be turned several degrees before the wheels begin to move, it indicates wear in the gear teeth, bushings, or ball joints.
• **Leaking Fluid:** On power steering units, leaks from the seals (especially around the input shaft or tie rod boots on a rack) are a clear sign of wear or damage.
• **Grinding or Clunking Noises:** Internal mechanical wear or damage, such as broken teeth or worn bearings, will cause metallic grinding or clunking sounds, particularly when turning sharply.
• **Difficulty Steering (Hard Steering):** While this is often a power steering pump or fluid issue, it can be caused by binding within the steering gear itself.

5. Procedure for Making Critical Adjustments to Steering Gears

Making critical adjustments, particularly to recirculating ball steering boxes, is a highly technical task that should only be performed by experienced professionals. Rack-and-pinion units are generally non-adjustable in the field and require replacement if internal wear occurs.

Warning: Incorrect adjustment can lead to binding (making steering difficult) or excessive wear, compromising safety.

Recirculating Ball (Steering Box) Adjustment Focus:

1. **Over-Center Load:** The primary adjustment is the pitman shaft over-center preload. This controls the mesh between the ball nut and the sector gear.
2. **Procedure:** Adjustments are made using an adjustment screw and lock nut on the steering box cover, measuring the turning effort (in inch-pounds or Newton-meters) with a torque wrench while turning the steering wheel through the center position.
3. **Final Check:** The turning effort must fall within the manufacturer's specific tolerance to ensure tight steering without binding.

6. Tools Required to Perform Work on Steering Gears

Servicing steering gears—especially removal and replacement—requires specialized tools:

• **Pitman Arm Puller:** Essential for safely removing the pitman arm from a steering box without damage.
• **Tie Rod Separator/Remover:** To disconnect tie rods from the steering knuckles.
• **Torque Wrench:** Critical for ensuring all fasteners (mounting bolts, tie rod nuts) are tightened to factory specifications for safety.
• **Flare Nut Wrenches:** Required for disconnecting hydraulic power steering lines without rounding the fittings.
• **Inverted Flare Caps:** Used to plug lines and prevent power steering fluid from leaking and contaminating the work area.

7. How Does Power Steering Work with Steering Gears?

Power steering is a hydraulic (or electric) assist system integrated directly into the steering gear assembly.

• **Hydraulic System:** A pump (driven by the engine belt) provides pressurized fluid to the steering gear. When the driver turns the wheel, an internal rotary valve directs fluid pressure to the cylinder on one side of the gear (rack or piston). This pressure assists the driver's manual effort, making the turning easier.
• **Torsion Bar Role:** In hydraulic systems, a torsion bar within the steering column measures the manual effort applied by the driver. The amount the bar twists dictates how much hydraulic pressure the rotary valve applies, ensuring proportional assist.
• **Electric Power Steering (EPS):** In modern vehicles, an electric motor directly assists the gear (often rack-and-pinion). This eliminates the need for a hydraulic pump and fluid.

8. Additional Work Required When Servicing a Steering Gear

If you are replacing or servicing a power steering gear (hydraulic type), the following essential steps must be performed:

• **System Flushing:** Before connecting the new gear, the entire power steering system (hoses, cooler, and pump) should be flushed with new fluid to remove contaminants, metal shavings, and debris from the old, worn gear.
• **Fluid Replacement:** Use only the OEM-specified power steering fluid (ATF, proprietary PSF, or specific hydraulic oil).
• **Air Bleeding:** After installation, the system must be meticulously bled to remove all trapped air, which can cause noisy operation, inconsistent assist, and damage to the new gear or pump.
• **Alignment Check:** Any time a steering gear or tie rods are replaced, a professional wheel alignment is mandatory to ensure proper steering angle and prevent premature tire wear.

9. Most Common Steering Gear Problems and Recommended Corrections

Problem: Steering Play (Loose Steering)

**Cause:** Wear in the internal gear components, worn tie rod ends, or loose mounting bolts.

**Correction:** Inspect linkages first. If play is traced to the internal gear, **replacement is the most reliable solution** for both rack and pinion and recirculating ball systems.

Problem: Power Steering Fluid Leakage

**Cause:** Failed hydraulic seals on the input shaft, pressure lines, or the internal piston.

**Correction:** Determine the source. If the leak is from the gear housing, replacement of the entire gear is usually recommended. A seal kit replacement can be attempted but is time-consuming and prone to failure if internal shafts are scored.

Problem: Hard/Heavy Steering

**Cause:** Low or contaminated fluid, failed power steering pump, or internal binding/scoring within the gear.

**Correction:** Check fluid level and condition first. If the pump output is good, then internal wear or corrosion in the steering gear is likely, requiring replacement.