1988-1993 Ford Taurus & Mercury Sable Front Knee/Knuckle: Diagnosing Noises and Replacement Guide

Symptoms of a Failing Front Knee or Wheel Bearing

Failures in the front knee assembly typically manifest as either a worn wheel bearing or, less commonly, a physically damaged knuckle. The symptoms for each are distinct.

Noises and Vibrations That Indicate Failure

• Grinding, Roaring, or Humming Noise: This is the classic sign of a bad wheel bearing. The noise is typically speed-dependent, becoming louder as you drive faster, often starting around 30 mph. It may sound like aggressive tire noise. A key diagnostic trick is to notice if the sound changes when you turn. For example, a failing bearing on the right side will often get louder when you turn left (loading the right side) and quieter when you turn right.
• Clunking or Popping Sounds: A clunk or pop, especially at low speeds when turning or going over bumps, often points to a worn lower ball joint, which connects the control arm to the bottom of the knuckle. While not part of the knuckle itself, it's a critical connection point and a common source of front-end noise.
• Vague or Loose Steering: If the steering feels sloppy or wanders, it can be a sign of excessive play in a worn wheel bearing or ball joint.
• Vehicle Pulling to One Side: A vehicle that pulls to one side, especially if an alignment doesn't fix it, can indicate a bent steering knuckle, usually from hitting a curb or a major pothole.
• Uneven Tire Wear: A damaged or bent knuckle will alter the wheel's alignment angles (camber, toe, and caster), causing rapid and uneven wear on the inside or outside edge of a tire.

How to Diagnose the Problem

Before buying parts, you can perform a few simple checks to pinpoint the issue.

1. The Wiggle Test: Safely raise the front of the vehicle and support it on jack stands. Grab the tire at the 12 o'clock and 6 o'clock positions and try to rock it in and out. Any noticeable play or clunking movement indicates a worn wheel bearing. Shaking the wheel at 3 and 9 o'clock can reveal a worn tie rod end.
2. The Spin Test: With the wheel still in the air, spin it by hand and listen closely. A good bearing will be nearly silent, while a bad one will sound rough, gritty, or make a grinding noise. You may also feel the roughness through the suspension spring if you rest a hand on it while spinning the wheel.
3. Visual Inspection: Look for visible cracks on the knuckle, especially around the mounting points for the strut and ball joint. Also check for a torn boot on the lower ball joint or tie rod end, which allows grease to escape and dirt to enter, causing premature wear.

Known Issues, TSBs, and Recalls for 1988-1993 Taurus & Sable

These vehicles have several well-documented issues, particularly related to corrosion in regions that use road salt.

• TSB 95-3-4 - Front End Clunking: Ford issued a Technical Service Bulletin for a "rattling" or "clunking" noise from the front end caused by a loose front tension strut bushing retainer in the subframe. The fix involves welding the retainer to the crossmember. This noise can be mistaken for a bad ball joint or strut mount.
• Recall 98V323000 - Subframe Corrosion: A major safety recall was issued for 1986-1995 Taurus and Sable models in salt-belt states. The rear subframe mount plate nuts can corrode and fail, potentially allowing the subframe (which holds the engine and transmission) to drop. This can cause a sudden and severe loss of steering control.
• Recall 91V134000 - Brake Rotor Corrosion: In salt-belt states, the original front brake rotors could corrode severely and fracture, leading to grinding noises and reduced braking power.

Buying a Used Front Knee / Knuckle Assembly

Since new OEM knuckles are largely discontinued and aftermarket options are scarce, a quality used OEM knuckle assembly is often the best choice for this repair, especially for DIYers without a press.

• What to Inspect: Physically inspect the used part before buying. Check the knuckle for any cracks, especially around the bearing bore and strut clamp area. Look for signs of heavy impact or bending. Spin the hub by hand; it should turn smoothly and silently with no roughness or side-to-side play.
• Mileage vs. Condition: While lower mileage is generally better, the physical condition of the bearing is what truly matters. A high-mileage part from a dry, southern climate may have a perfectly good bearing, while a lower-mileage part from a northern, salt-belt state could have a failed bearing. A hands-on inspection is more important than the odometer reading.
• Compatibility: Ensure you are getting the correct part for your vehicle. Knuckles are specific to the driver's side (left) and passenger's side (right). There may also be differences between models with and without ABS, and between standard models and the high-performance SHO. Cross-reference OEM part numbers when possible.
• Why Used OEM is a Good Option: A used OEM knuckle assembly saves you the significant labor and tool cost of pressing out an old bearing and pressing in a new one. The quality of the Ford factory casting is also typically superior to cheap aftermarket alternatives.

Replacement Overview & Torque Specs

Replacing the front knuckle is an involved job but is feasible for an experienced DIY mechanic. The basic steps involve removing the wheel, brake caliper and rotor, axle nut, and then disconnecting the tie rod end, lower ball joint, and the two bolts securing the knuckle to the strut.

An alignment is required after replacing a steering knuckle to ensure proper handling and prevent tire wear.

Related Parts to Consider Replacing

While you have the suspension apart, it's a good time to inspect and potentially replace other related wear items:

• Lower Ball Joint: If it's original, it's likely worn. They are relatively inexpensive and critical for safety.
• Outer Tie Rod End: You have to disconnect it anyway, making it an easy 'while you're in there' replacement.
• CV Axle Shaft: Inspect the rubber boots for any tears or leaking grease. A torn boot will lead to rapid CV joint failure.
• Sway Bar Links: These often cause clunking noises and are easy to replace at the same time.

Cost of Replacement

Prices can vary based on location and part quality. Since new OEM knuckles are generally unavailable, the comparison focuses on other options.

Frequently Asked Questions (FAQ)