2000-2004 Jaguar S-Type Front Knee Assembly: The Critical VIN M45254 Suspension Split

The Critical 2002.5 Suspension Change: VIN M45254

Before purchasing a front knee assembly for a 2000-2004 Jaguar S-Type, you must check the vehicle's VIN. Jaguar significantly redesigned the front suspension starting with the 2003 model year, often referred to as the '2002.5' update. This change occurred at VIN M45255. Parts are not interchangeable across this divide.

• Early Models (2000-2002, up to VIN M45254): These vehicles use a specific knuckle design with corresponding control arms and ball joints. The lower ball joint typically uses a 14mm thread.
• Late Models (2003-2004, from VIN M45255 onward): These models feature a revised knuckle, different control arms, and a different lower ball joint, which often has a 16mm thread.

Symptoms of a Failing Front Knee Assembly

Failure in the knee assembly usually involves the components attached to it, namely the wheel bearing and ball joints. The knuckle itself is a solid piece of metal that typically only fails from collision damage.

Noises and Vibrations

• Clunking or Knocking: A clunking or rattling sound, especially at low speeds over bumps, is a classic sign of a worn lower ball joint. This was a very common issue on early S-Types. Worn sway bar bushings or control arm bushings can also cause similar sounds.
• Grinding, Humming, or Whining: A continuous grinding or humming noise that changes with vehicle speed (but not engine RPM) strongly indicates a failed wheel bearing. The noise may get louder when turning in one direction, which loads the failing bearing.
• Creaking: A creaking sound when going over speed bumps or braking can point to worn front control arm hydro-bushings, as noted in a Jaguar Technical Service Bulletin (TSB #20408).

Steering and Handling Issues

• Vehicle Pulling: A bent knuckle (from hitting a curb or large pothole) or severely worn ball joints can cause the vehicle to pull to one side and make a proper wheel alignment impossible.
• Uneven Tire Wear: Bad ball joints or a bent knuckle can alter the suspension geometry, leading to accelerated wear on the inside or outside edges of the front tires.
• Loose Steering Feel: Excessive play in the ball joints or wheel bearing can translate to a vague or imprecise feeling in the steering wheel.

Known Issues, Recalls, and TSBs

NHTSA Recall 00V-359: Lower Ball Joint Failure Risk

For 2000-2001 S-Type models, Jaguar issued a critical safety recall because the front lower ball joint attaching nuts may not have been tightened correctly at the factory. This could cause the nut to loosen, leading to fatigue and fracture of the ball joint stud, which would result in a separation of the suspension and a loss of vehicle control. The remedy was for dealers to inspect the torque and, if loose, replace the entire vertical link (knuckle) assembly. When buying a used part from this era, be aware of this potential history.

Buying a Used Front Knee Assembly: What to Look For

A used OEM knee assembly is an excellent value, as the factory casting is very robust. The main concerns are the condition of the integrated wear items and ensuring compatibility.

1. Confirm the VIN Range: This is the most important step. Get the VIN from the donor vehicle and confirm if it is before or after the M45254 split to ensure it matches your car.
2. Inspect for Cracks: Carefully examine the entire knuckle for any hairline cracks, especially around the ball joint mounting points and where the brake caliper bolts on. Any cracks mean the part is unsafe and should be rejected. This is especially important as the part may have come from a vehicle involved in a collision.
3. Check the Wheel Bearing: A used knuckle will almost always come with the wheel hub and bearing installed. With the knuckle on the ground, try to spin the hub by hand. It should be smooth and silent. If you feel any roughness, grinding, or hear noise, the bearing is bad and will need to be replaced. Also, try to wiggle the hub side-to-side; there should be zero play.
4. Examine Ball Joint Tapers: Look at the tapered holes where the upper control arm, lower ball joint, and tie rod end mount. Ensure they are not damaged, oval-shaped, or cracked.
5. Mileage vs. Condition: While lower mileage is generally better, the physical condition is more important. A high-mileage knuckle with a good bearing is a better buy than a low-mileage one with a bad bearing. Expect to replace the wheel bearing on most used units as a matter of course; consider a smooth, tight bearing a bonus.

Cost Comparison for Front Knee/Knuckle Replacement

Prices can vary significantly based on the year of your S-Type and the source of the part. Labor for a complete knuckle replacement is typically less than replacing individual pressed-in components like a wheel bearing or ball joint.

Related Parts to Inspect

When the knee assembly is removed, you have easy access to several other suspension components. It's wise to inspect them for wear.

• Upper and Lower Control Arms: Check the bushings for cracks or deterioration and the ball joints for torn boots or excessive play.
• Tie Rod Ends: Check for any play in the joint or torn rubber boots.
• Sway Bar Links and Bushings: These are common sources of noise and are inexpensive to replace.
• ABS Sensor and Wire: Ensure the sensor is not damaged and the wire is not frayed or broken.

Frequently Asked Questions (FAQ)