2017-2019 Infiniti QX30 Steering Knuckle: The Mercedes Connection and FWD vs. AWD Fitment

The Mercedes-Benz Connection

The 2017-2019 Infiniti QX30 is based on the same platform as the Mercedes-Benz GLA-Class (X156 chassis). Because of this, many parts are shared between the two vehicles, including the steering knuckle. The OEM Infiniti part numbers 40014-5DA0A and its replacement, 40014-HG00A, cross-reference to the Mercedes-Benz part number A2463320200. This means a steering knuckle from a corresponding 2015-2020 Mercedes-Benz GLA250 or 2014-2019 CLA250 (without the Sport Edition package) can be a direct replacement. This is valuable information when searching for used parts, as it significantly widens the available inventory.

Symptoms of a Failing Steering Knuckle

A steering knuckle is a robust piece of metal and typically only fails due to impact (like hitting a curb or large pothole) or when related components, like the wheel bearing, seize. Here are the most common symptoms:

• Clunking or Popping Noises: You may hear clunking, popping, or knocking sounds, especially when turning at low speeds or going over bumps. This can be caused by a worn ball joint moving within its socket on the knuckle or by the knuckle itself being cracked.
• Grinding or Humming Noises: A constant grinding, humming, or roaring noise that changes with vehicle speed is a classic sign of a bad wheel bearing. Since the wheel bearing is pressed into the knuckle, they are often replaced as an assembly.
• Steering and Alignment Issues: A bent or damaged knuckle will alter the suspension geometry. This can cause the vehicle to pull to one side, the steering wheel to be off-center, or create a loose or vague feeling in the steering. You may also notice uneven or premature tire wear.
• Vibrations: A damaged knuckle can cause vibrations felt in the steering wheel, especially at highway speeds.

Known Issues, TSBs, and Recalls

While there are no recalls specifically for the steering knuckle on the 2017-2019 Infiniti QX30, there is a significant steering-related recall to be aware of.

• NHTSA Recall #21V419000 (Infiniti Campaign ID PG1CF): Issued for some 2017 QX30 vehicles, this recall addresses an issue where the lower steering shaft could separate from the universal joint, leading to a complete loss of steering control. Symptoms include abnormal noises and an imprecise steering feel. The remedy is to replace the lower steering shaft.
• NHTSA Recall #17V691000: Affects some 2017-2018 QX30 models where the driver's airbag could deploy unexpectedly due to insufficient grounding of steering components.

No Technical Service Bulletins (TSBs) directly related to steering knuckle failure were found. Most owner complaints revolve around clunking noises which are often attributed to related suspension parts like ball joints, sway bar links, or struts.

Buying a Used Steering Knuckle Assembly

A used OEM steering knuckle from a low-mileage vehicle can be an excellent value compared to a new part and is often superior in quality to cheap aftermarket alternatives. Here’s what to look for:

• Verify Compatibility: This is the most critical step. Confirm whether your QX30 is FWD or AWD and ensure the donor vehicle matches. Part numbers for FWD and AWD models are different. Also, remember you can search for parts from compatible Mercedes-Benz GLA250 and CLA250 models.
• Physical Inspection: Carefully inspect the entire knuckle for any signs of cracks, especially around the mounting points for the strut, control arm, and tie rod. Check for any bending or warping. Even a slight bend from an accident can make the part unusable and prevent proper wheel alignment.
• Check the Wheel Bearing: If the used knuckle includes the wheel hub and bearing, try to spin it by hand. It should rotate smoothly and silently. Any roughness, grinding, or play indicates the bearing is bad and will need to be replaced—a job that requires a hydraulic press.
• Condition of Mating Surfaces: Look for heavy rust or corrosion, especially where the wheel bearing/hub assembly mounts. If the hub is seized into the knuckle due to rust, it can make future service impossible, sometimes requiring replacement of the entire knuckle just to service the bearing.
• Mileage: The knuckle itself doesn't wear out with mileage, but the wheel bearing does. Prioritize assemblies from vehicles with lower mileage (ideally under 80,000 miles) to maximize the life of the included bearing.

Cost Comparison

Prices can vary based on location and supplier. Labor costs for replacement typically range from $240 to $353 per side. A wheel alignment is mandatory after replacement and adds to the total cost.

Replacement Overview

Replacing a steering knuckle is an advanced job that requires significant disassembly of the suspension and brake systems. It is not recommended for beginners.

1. The vehicle must be safely lifted and supported on jack stands.
2. The wheel, brake caliper, caliper bracket, and brake rotor are removed.
3. The axle nut is removed to allow the CV axle to be separated from the hub.
4. The tie rod end, lower ball joint, and strut bolts are disconnected from the knuckle.
5. The entire knuckle assembly can then be removed from the vehicle.

Related Parts

When replacing a steering knuckle, it's a good time to inspect other nearby components, as the labor overlaps significantly. Consider replacing:

• Lower Control Arm / Ball Joint
• Tie Rod End
• Wheel Bearing and Hub (if not included with the knuckle)
• CV Axle
• Strut Assembly

Frequently Asked Questions (FAQ)

Technical Specifications and Part Numbers