Steering Rack (Rack and Pinion): What It Does and When to Replace It

What Is a Steering Rack?

The steering rack (formally the rack and pinion steering gear) is the central component of your car's steering system. It converts the rotational movement of the steering wheel into the lateral (side-to-side) movement needed to turn the front wheels.

When you turn the steering wheel, a shaft runs down to the rack via the steering column. A small pinion gear at the end of the shaft meshes with a toothed rack (a flat bar with teeth). As the pinion rotates, it moves the rack left or right, which pushes or pulls the tie rod ends and turns the wheels.

Power Steering: Hydraulic vs. Electric

Most modern NZ vehicles have power-assisted steering to reduce effort, especially at low speeds and when parking. There are two types:

Hydraulic Power Steering (HPAS)

Uses a power steering pump (see power steering pump) to pressurise fluid that assists the rack. Older technology but very common on Japanese imports. The rack has internal hydraulic chambers that amplify your steering input.

Electric Power Steering (EPS)

An electric motor — either on the column or directly on the rack — provides assistance. No fluid required. Common on vehicles from mid-2000s onwards. Simpler, more fuel-efficient, but the motor can fail.

Signs of a Failing Steering Rack

Fluid Leaks

On hydraulic racks, power steering fluid leaking from the rack is the most common failure. Look for:

• Oily residue on the rack (visible under the car, behind the front wheels)
• Power steering fluid level dropping
• Possible groaning noise from the pump when turning

A minor leak can sometimes be managed with a rack seal replacement. A severely worn or cracked rack body requires full replacement.

Knocking or Clunking

A knock or clunk from the steering when going over bumps, or play felt in the steering wheel over rough roads, indicates worn rack bushes, loose rack mounting, or internal wear in the rack itself.

Loose or Vague Centre Feel

The steering feels disconnected or loose around the straight-ahead position — small steering inputs don't produce crisp response. This "dead zone" in the steering centre is a sign of worn rack internals.

Heavy Steering

On hydraulic systems, heavier-than-normal steering (especially at low speed) may indicate a failing pump — but it can also indicate an internal rack fault blocking fluid flow.

Pulling to One Side

If the rack is stuck or binding on one side, the car may pull in that direction.

WoF Relevance

Steering rack issues are relevant to WoF in several ways:

• Fluid leaks from the rack onto tyres or other components can cause a WoF fail
• Excessive play in the steering system (including a loose or worn rack) fails a WoF
• A rack that binds or sticks affects vehicle control — fail

NZTA steering inspections check overall play and feel, so a badly worn rack will be picked up.

Can a Rack Be Repaired vs. Replaced?

• Minor leaks: A rack seal kit can be fitted, costing $300–$600 less than full replacement — but only if the rack body and gear surfaces are in good condition.
• Worn internals, bent rack, significant play: Full replacement is required. Remanufactured racks are widely available and often the most cost-effective path.
• Electric racks: Motor replacement or rack replacement depending on the fault.

NZ Cost to Replace

Wheel alignment is mandatory after any steering rack work — the toe angle changes with a new or rebuilt rack.

When to Book a Mechanic

• Power steering fluid level is dropping without a visible external cause
• Oily staining visible on the rack or under the front of the car
• Steering has developed a loose feel or dead zone around straight-ahead
• You hear clunking from the steering when driving on uneven roads
• WoF inspection noted steering rack play or leaks

Further Reading

• Find a mechanic near you
• Tie rod ends: what they do and why they fail
• Power steering pump: what it does and signs it's failing
• Power steering fluid: what it does and when to top it up