Aston Martin DB9, Vantage, DBS & Virage Rear Knuckle Guide (2004-2018)
Diagnosing humming noises and rear-end instability on the VH-platform Aston Martins and ensuring you buy the correct replacement rear knuckle.
- The most common failure is the wheel bearing inside the knuckle, causing a humming noise. The knuckle itself usually only fails from an impact.
- Part compatibility is critical. You MUST verify if your car has the early (4G43- prefix) or late (8D33- prefix) style knuckle before buying.
- When buying a used knuckle, always inspect for cracks and plan to install a new wheel bearing (part # 4G43-2B663-AD) before installation.
- A professional four-wheel alignment is mandatory after replacing a rear knuckle to ensure safety and prevent rapid tire wear.
Symptoms of a Failing Rear Knuckle or Bearing
On the 2004-2016 Aston Martin DB9, 2006-2018 V8 Vantage, 2012-2013 Virage, 2007-2014 DBS, and 2010-2018 V12 Vantage, the knuckle itself is a robust component. Failure is typically caused by a significant impact, like hitting a curb or a deep pothole. More often, the part that fails is the wheel bearing housed within the knuckle.
- Humming or Grinding Noise: This is the most common symptom and almost always indicates a failed wheel bearing, not the knuckle itself. The noise comes from the rear of the car, starts as a faint hum, and progresses to a louder roar or grind. It gets louder with increased speed and may change pitch when turning.
- Vibration or Wobble: A vibration felt through the seat or floor, especially at highway speeds, can be caused by a worn wheel bearing or a bent knuckle.
- Vehicle Pulling to One Side: If the knuckle is bent from an impact, it will throw off the rear wheel alignment, causing the car to drift or pull to one side. This issue cannot be corrected with a standard alignment.
- Uneven Tire Wear: A bent knuckle will cause rapid and uneven wear on the inner or outer edge of the corresponding tire due to the incorrect alignment angle.
- Clunking or Popping Sounds: A sharp clunk or pop when going over bumps or during turns can indicate a crack in the knuckle or excessive play from worn suspension mounting points.
Known Issues and Part Number Compatibility
There are no specific recalls or widespread factory defects concerning the rear knuckles on these Aston Martin models. The primary issue for buyers and technicians is ensuring compatibility, as different parts were used during the long production run.
Compatibility Warning: Aston Martin used at least two different styles of rear knuckles on these vehicles. Early DB9 and V8 Vantage models (reportedly pre-VIN GD08958 on the DB9) used a knuckle with a part number prefix of 4G43-. Later models switched to an updated design with a prefix of 8D33-. The parts are not interchangeable. Before purchasing, you must visually inspect your existing knuckle and verify the part number cast into it.
Key Part Numbers to Know:
- Later Style Rear Knuckle (Left): 8D33-5A971-AB
- Later Style Rear Knuckle (Right): 8D33-5A970-AB
- Wheel Hub & Bearing Assembly: 4G43-2B663-AD. This is the bearing unit that presses into the knuckle and is a common failure point. 🎬 Watch this step-by-step guide on replacing the rear hub. It is used in both early and late knuckles.
The change in knuckle design was likely to accommodate changes in brake systems (especially for 'S' or V12 models with larger brakes), or for minor geometry improvements. Using the wrong knuckle can result in improper brake caliper fitment or incorrect suspension geometry.
Buying a Used Rear Knuckle: What to Check
A used OEM knuckle is an excellent, cost-effective alternative to a new dealer part, provided it is inspected carefully. Since these are not high-wear items, a good used part is functionally identical to a new one.
🎬 See a full suspension overhaul for these Vantage models.- Check for Cracks: This is the most important check. Thoroughly inspect the entire part, especially around the mounting bosses for the control arms and the main bore where the bearing is pressed in. Any visible cracks mean the part is unsafe and should be rejected.
- Inspect for Bends or Impact Damage: Look for scrapes, gouges, or any signs of a heavy impact. Place the knuckle on a flat surface to check for warping. A bent knuckle will cause persistent alignment problems.
- Verify the Part Number: As mentioned, this is critical. Locate the number cast into the aluminum (e.g., "8D33-5A971-AB") and ensure it matches the part you are replacing.
- Examine Mounting Holes: The tapered holes for the ball joints and toe link should be perfectly round and smooth. If they are oval-shaped, damaged, or corroded, the connection will not be secure.
- Assume the Bearing is Bad: Most used knuckles will come with the old wheel hub and bearing still installed. It is highly recommended to have a new wheel bearing (part number 4G43-2B663-AD) pressed into the used knuckle by a machine shop before you begin the installation. Installing a used knuckle with an old bearing is asking for trouble.
Pro Tip: When a wheel bearing fails, it often only requires replacing the bearing assembly (4G43-2B663-AD), not the entire knuckle. The knuckle only needs to be replaced if it is physically cracked or bent from an impact.
Replacement Cost Comparison
Replacing a rear knuckle is a labor-intensive job. The cost of parts can vary dramatically between new OEM, used OEM, and the separate bearing assembly.
| Part or Service | Estimated Cost |
|---|---|
| New OEM Rear Knuckle (One Side) | $1,100 - $1,200 |
| Used OEM Rear Knuckle (One Side) | $150 - $400 |
| New OEM Wheel Hub & Bearing Assembly | $450 - $550 |
| New Aftermarket Wheel Hub & Bearing Assembly | $200 - $300 |
| Shop Labor (Knuckle & Bearing Replacement) | $500 - $1,100 |
| Mandatory Wheel Alignment | $200 - $300 |
Installation Overview & Difficulty
Replacing the rear knuckle is an advanced job not recommended for beginners. It requires significant disassembly of the suspension and specialized tools.
- Difficulty Rating: 4 out of 5
- Procedure: The process involves removing the wheel, brake caliper and rotor, the main 36mm axle nut, and disconnecting the upper control arm, 🎬 Watch how to remove the rear lower wishbone assembly. lower control arm, and toe link from the knuckle. The half-shaft (axle) must then be carefully pressed out of the hub.
- Special Tools: A hydraulic press is needed to install the new bearing into the knuckle. A heavy-duty torque wrench is required for the 300 Nm (221 lb-ft) axle nut.
- Mandatory Final Step: A full four-wheel alignment is absolutely required after the job is complete to ensure safety, proper handling, and to prevent immediate tire damage.
Frequently Asked Questions (FAQ)
Do I need to replace the knuckle if I just have a humming noise?
No, a humming or grinding noise almost always points to a bad wheel bearing. In this case, you can have a shop press the old bearing out of your existing knuckle and press a new one in, which is much cheaper than replacing the entire knuckle assembly.
Can I use a knuckle from a V8 Vantage on my DB9?
Yes, provided the part numbers match. These cars share the same fundamental VH platform architecture, and many suspension parts are interchangeable. The most important factor is matching the part number prefix (e.g., 8D33-) from your old part to the new one to ensure correct brake and suspension geometry.
Is it safe to drive with a bad rear knuckle or bearing?
Driving with a noisy wheel bearing is not recommended for long distances as it can eventually seize or collapse, potentially causing a loss of vehicle control. Driving with a known cracked or bent knuckle is extremely dangerous and should be avoided, as a complete failure could lead to the wheel detaching from the vehicle.
Why is a wheel alignment mandatory after replacement?
The knuckle is the central component that dictates the wheel's alignment angles (camber and toe). Even a tiny variation in a replacement part or the reassembly process will alter these angles. Skipping the alignment will result in poor handling, instability, and will destroy your rear tires in a very short time.
Helpful Videos
Technical Specifications
OEM Part Numbers: 8D33-5A971-AB (Knuckle, Rear Left) 8D33-5A970-AB (Knuckle, Rear Right) 4G43-2B663-AD (Hub & Bearing Assembly)
Material: Cast Aluminum. The knuckle houses the replaceable 4G43-2B663-AD wheel hub and bearing assembly.
We Have This Part in Stock
The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
- Aston Martin DB9:
- Aston Martin V8 Vantage:
- Aston Martin Virage:
- Aston Martin DBS:
- Aston Martin V12 Vantage:
- 🎬 Helpful Videos
- 🛍️ Shop This Part
- Symptoms of a Failing Rear Knuckle or Bearing
- Known Issues and Part Number Compatibility
- Key Part Numbers to Know:
- Buying a Used Rear Knuckle: What to Check
- Replacement Cost Comparison
- Installation Overview & Difficulty
- Frequently Asked Questions (FAQ)
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