2004 Infiniti G35 Steering Knuckle: Decoding RWD, AWD & Mid-Year Changes

Key Compatibility Warnings for the 2004 Infiniti G35

The 2004 model year for the Infiniti G35 is known for having mid-year production changes, which can make sourcing the correct steering knuckle assembly challenging. There are two primary distinctions you must verify before purchasing a replacement.

1. Rear-Wheel Drive (RWD) vs. All-Wheel Drive (AWD/G35X)

The most significant difference is between the RWD and AWD (badged as 'X') models. The front suspension components are not interchangeable. The AWD knuckle is designed to accommodate a front drive axle passing through it, while the RWD version is not. Always confirm your vehicle's drivetrain before ordering.

2. Mid-Year Production Split (2004 vs. 2004.5)

Infiniti made changes to the G35 during the 2004 model year, creating what owners refer to as an '04.5' model. These changes can affect suspension components. For coupes, the changeover point is generally considered to be VINs ending in 800001 and higher. For sedans, production dates around January or February 2004 mark the transition. While the knuckle itself may seem similar, related components like control arms and ball joints were altered. It is essential to match the part to your vehicle's specific production date or VIN.

Symptoms of a Failing Steering Knuckle Assembly

The steering knuckle itself is a robust piece of forged or cast metal. Failure usually comes from two sources: impact damage (bending or cracking) or the failure of integrated components like the lower ball joint or the wheel hub/bearing assembly.

Noises and Vibrations

• Clunking or Popping: A clunking or popping sound, especially when driving over bumps or turning at low speeds, often points to a worn-out lower ball joint, which is part of the knuckle assembly.
• Grinding, Roaring, or Whining: A noise that changes with vehicle speed and may get louder or quieter when turning is a classic symptom of a bad wheel bearing. On the G35, the wheel bearing hub assembly bolts to the knuckle.
• Squealing When Turning: This can indicate that the ball joint has lost its lubrication and is failing, or that a bent knuckle is causing alignment issues.

Steering and Handling Issues

• Vague or Loose Steering: Excessive play in the steering wheel can be caused by a worn ball joint.
• Vehicle Pulling to One Side: A bent steering knuckle from hitting a curb or pothole will throw off the wheel alignment and cause the car to pull. This may be a pull that a standard alignment cannot correct.
• Uneven Tire Wear: A bad knuckle or ball joint will alter the wheel's camber or toe, causing rapid and uneven wear on the inner or outer edge of the tire.

Known Issues, TSBs, and Recalls

While there are no specific recalls for the 2004 G35 steering knuckle itself, several related service bulletins and common problems are relevant.

• TSB ITB08-013a: This technical service bulletin addresses a common knocking noise from the front suspension when driving over bumps. The cause is often a failed bushing in the compression rod, which attaches to the steering knuckle. While this isn't a knuckle failure, the noise is frequently misdiagnosed, and the compression rod should be inspected during any knuckle replacement.
• Recalls: The 2004 G35 had several recalls, but none directly involve the steering knuckle. Recalls were issued for issues like passenger airbag sensors, fuel hoses, and engine sensors.
• Common Failure Point: The compression rod bushings are a well-documented weak point on the G35/350Z platform, leading to clunking noises. Many owners replace the entire compression arm or upgrade to firmer aftermarket bushings.
🎬 Watch this video to diagnose and fix front suspension clunking noises.

Buying a Used 2004 G35 Steering Knuckle Assembly

A recycled OEM steering knuckle is often a smart choice, as the original factory part's material quality and geometry are superior to many cheap aftermarket alternatives. However, careful inspection is critical.

What to Inspect

• Check for Cracks or Bends: Visually inspect the entire knuckle, paying close attention to the mounting points for the control arms, tie rod, and caliper. Any sign of cracking or bending means the part is junk. Compare it to photos of a known-good part if possible.
• Examine the Ball Joint Taper: The hole where the lower ball joint mounts is a tapered fit. Check this area for any distortion, excessive corrosion, or signs of being 'wallowed out'. A damaged taper means the knuckle should be replaced.
• Condition of Included Components: A used assembly will likely come with the lower ball joint and wheel hub. Assume these are wear items. Check the ball joint's rubber boot for tears. If the boot is torn, the joint is likely contaminated and will fail soon. Plan on potentially replacing the wheel bearing, as its remaining life is unknown.
• Verify Part Numbers and Compatibility: Given the RWD/AWD and mid-year splits, this is the most important step. Get the VIN from the donor vehicle if possible to confirm its specifications. Part number 40015-AL550 is a common replacement for the earlier 40015-AL510 for the RWD models.

Replacement Overview and Torque Specs

Replacing the steering knuckle is a significant job that requires disassembling most of the front suspension. It is feasible for an experienced DIY mechanic but can be challenging.

Related Parts to Inspect and Replace

While the knuckle is out, it's the perfect time to inspect or replace other nearby components:

• Wheel Hub/Bearing Assembly: It's highly recommended to replace the wheel bearing when replacing the knuckle, especially on a higher-mileage vehicle.
🎬 See this step-by-step wheel bearing and hub replacement walkthrough.
• Compression Rod: Inspect the bushings for tears or leaks.
• Upper Control Arm: Check the ball joint and bushings for wear.
• Tie Rod End: Check for play.
• Axle Nut: This is a one-time-use item and MUST be replaced.

Torque Specifications

Using correct torque specs is critical for safety. While specs can vary slightly by model and source, these are commonly cited values for the G35/350Z platform. Always consult the factory service manual for your specific vehicle.

Cost Comparison

Prices can vary significantly based on brand, location, and condition.

Frequently Asked Questions (FAQ)