FORMULA, SUPERPRO Power Steering Racks with Fitting Position Front and Rear, Front Axle

A power steering rack converts the turning of the steering wheel into the side-to-side movement that steers the front wheels, with power assistance to reduce the effort needed. On bakkies and independent front suspension 4WDs, the rack is the heart of the steering system, and when it wears or leaks, the result can be heavy or uneven steering, knocks through the wheel and fluid loss. A replacement rack restores the steering when the existing unit is beyond repair. Racks are specific to each vehicle, so use the vehicle search to find power steering racks to suit your 4WD.

What Does a Power Steering Rack Do?

A rack and pinion steering system has two main parts. The pinion is a small gear on the end of the steering shaft, and the rack is a toothed bar that runs across the front of the vehicle inside a housing. When the steering wheel turns, the pinion turns and moves the rack left or right. The rack ends and tie rods at each end of the rack transfer that movement to the steering knuckles, turning the wheels.

Power assistance makes the rack easier to move. Without it, steering a heavy 4WD with large tyres at low speed would take considerable effort. The power steering system adds force to the rack in the direction the driver is turning, so the steering feels lighter while still giving the driver control.

Hydraulic and Electric Power Steering

There are two main types of power assistance. Hydraulic power steering uses a pump, usually driven by the engine's drive belt, to push fluid through hoses to the rack. Valves in the rack direct pressurised fluid to one side of a piston inside the rack housing, adding force in the direction of the turn.

Electric power steering uses an electric motor instead, mounted on the steering column or on the rack itself, controlled by an electronic module that reads the steering input. There is no fluid, pump or hoses. Many older and some current 4WDs use hydraulic systems, while many newer vehicles use electric assistance. Check which type your vehicle uses before ordering a rack, since the two are not interchangeable.

Signs Your Steering Rack May Be Worn

On hydraulic racks, fluid leaks are one of the most common signs. Fluid can leak from the seals at each end of the rack and collect inside the rubber boots that cover the rack ends, so a boot that is wet or bulging with fluid points to a leaking seal. A power steering fluid level that keeps dropping is another indicator.

Other signs include steering that feels heavier in one direction than the other, steering that is heavy or notchy when cold and eases as it warms up, a knocking or clunking felt through the steering wheel over bumps, and play in the steering where the wheel moves slightly before the vehicle responds. Some worn racks also make a groaning or whining noise when turning, particularly at full lock.

Other Possible Causes

Steering problems are not always caused by the rack. A failing power steering pump, low or contaminated fluid, a slipping drive belt, leaking hoses, worn tie rod ends, worn rack ends and worn rack mount bushes can all produce similar symptoms. Have a technician diagnose the cause before replacing the rack, since a new rack will not fix a pump, hose or linkage fault.

Replace or Recondition a Steering Rack?

When a rack has failed, the choices are usually to reseal or recondition the existing rack, fit a reconditioned rack, or fit a replacement rack. Resealing can fix leaks when the rack's internal surfaces are still in good condition, but it is less effective if the rack bar or housing is worn or scored.

A replacement rack is often chosen when wear is advanced, when reconditioning would take the vehicle off the road for longer, or when the existing rack is damaged. The right choice depends on the condition of the original rack, how long the vehicle can be off the road and the owner's plans for the vehicle. A technician can assess the rack and advise which approach suits it.

How Lifts and Larger Tyres Affect the Rack

A suspension lift on an independent front suspension 4WD changes the angle of the tie rods relative to the rack. Steeper tie rod angles can increase the load on the rack ends and the rack itself, and they can contribute to bump steer, where the wheels steer slightly as the suspension moves.

Larger, heavier tyres add to the load on the rack. A bigger tyre increases the leverage acting on the steering when a wheel hits an obstacle, and wider tyres take more effort to turn when parking or manoeuvring at low speed. Over time, those loads can accelerate wear on the rack's internal seals and bushes, as well as on the rack mounts and rack ends. Checking the steering system more often is worthwhile on a lifted 4WD with larger tyres.

Protecting a Steering Rack From Damage

A few habits help a steering rack last. Avoid holding the steering at full lock for extended periods, particularly with the engine running and the vehicle stationary, since this puts the power steering system under maximum pressure. On hydraulic systems, keep the fluid at the correct level, use the fluid type specified by the vehicle manufacturer, and have the fluid changed at the recommended intervals.

Check the rack boots whenever the vehicle is serviced. A torn boot lets water, mud and grit reach the rack bar and its seals, causing rapid wear. Replacing a damaged boot early is far simpler than replacing a rack. After deep water crossings or muddy driving, have the boots and rack ends checked for damage or contamination.

Replacing a Power Steering Rack: An Overview

Replacing a steering rack is safety-critical work, and it should be carried out by a qualified technician. The vehicle is supported on rated stands, the tie rod ends are separated from the steering knuckles, the steering shaft is disconnected from the pinion, and on hydraulic systems the fluid lines are disconnected from the rack. The rack is then unbolted from its mounts and removed.

The replacement rack is fitted with its mounting bolts tightened to the manufacturer's torque specification. Depending on how the rack is supplied, the rack ends and tie rod ends may need to be transferred from the old rack or replaced. Hydraulic systems need to be refilled with the specified fluid and bled to remove air, following the manufacturer's procedure.

A wheel alignment is required after fitting, since a rack replacement affects toe and the steering wheel centre. On vehicles with stability control, the steering angle sensor may need to be recalibrated with a diagnostic tool after the steering has been worked on.

Choosing the Right Power Steering Rack

Steering racks are specific to the vehicle. Mounting points, rack length, hydraulic line fittings, electrical connectors and the steering ratio all vary between makes, models, model years and sometimes variants. Confirm your vehicle's make, model, year and power steering type before ordering, and check whether the rack is supplied with or without rack ends and tie rod ends.

Shop Power Steering Racks with Formula 4x4

Power steering racks are part of the Formula 4x4 steering parts range, and fresh rack and pinion bushes stop a new rack shifting in its mounts.

Start by confirming that the rack is the source of the steering problem rather than the pump, fluid, hoses or linkage. Search by your vehicle to find power steering racks to suit it, and plan for a wheel alignment and, on hydraulic systems, a fluid bleed after fitting. If you are unsure which part your vehicle needs, contact the Formula 4x4 team.