1990-1997 Lexus LS400 Suspension Struts: Clunks, Leaks, and Replacement Guide
This guide covers how to diagnose failing struts on your first-generation LS400, avoid common compatibility mistakes, and restore that legendary smooth ride.
- The most critical step is to confirm your LS400 has standard coil suspension, not the optional air suspension, as the parts are not interchangeable.
- Clunking noises are the most common failure symptom, often caused by the strut itself, the top mount, or related (and commonly worn) strut rod bushings.
- When buying used, a leak-free strut is the top priority. A dry, high-mileage strut is better than a low-mileage one that's leaking fluid.
- Always replace struts in pairs (both front or both rear) and get a professional wheel alignment immediately after installation to prevent handling issues and tire damage.
Symptoms of a Failing Suspension Strut
A failing suspension strut on a Lexus LS400 will noticeably degrade its ride quality and introduce noises. Symptoms are often gradual at first but become more pronounced over time.
Noises: Clunking, Popping, and Rattling
The most common sign of a bad strut is noise, especially over bumps. You might hear a heavy "clunk" or "bang" when driving over potholes or uneven road surfaces. This often points to worn-out internal components of the shock absorber or failure of the top strut mount. A popping or groaning sound when turning the steering wheel at low speeds can also indicate a problem with the strut mount bearing. Forum users frequently trace front-end clunks on the LS400 to worn strut rod bushings, which are a related but separate component that should be inspected at the same time.
Poor Ride Quality and Handling
The LS400 is known for its smooth ride; a failing strut will make the car feel bouncy and unstable, like riding on a "jello-mold". Other symptoms include:
- Excessive Bouncing: After hitting a bump, the car continues to bounce up and down.
- Nose-Diving: The front of the car dips excessively when you apply the brakes.
- Body Roll: The car leans more than usual during turns.
- Drifting or Instability: The car may feel unstable or drift on windy days, a sign that the worn suspension can't keep the car controlled.
Visual Signs of Failure
A visual inspection can often confirm a bad strut. Look for:
- Fluid Leaks: Oily or wet patches on the body of the shock absorber indicate that the seals have failed and fluid has leaked out. A strut with significant fluid loss cannot dampen vibrations effectively.
- Uneven Tire Wear: Worn struts can cause tires to bounce, leading to scalloped or "cupped" wear patterns on the tire tread.
- Damaged Components: Check the rubber strut mount at the top of the assembly for cracks or deterioration. Also inspect the dust boot for tears, as this can allow dirt and debris to damage the strut's seals.
Critical: Standard vs. Factory Air Suspension
The single most important factor when replacing struts on a 1990-1997 LS400 is identifying the suspension type. These vehicles were available with either a standard coil spring suspension or an optional, electronically controlled air suspension. The parts are NOT interchangeable. This guide and the parts discussed are for vehicles WITHOUT the factory air suspension. Installing standard struts on an air suspension car requires a full conversion kit and is a much more involved job.
Known Issues, TSBs, and Recalls
For the 1990-1997 model years, there are no specific recalls or Technical Service Bulletins (TSBs) from Lexus directly addressing the standard suspension struts. However, there is a TSB for a ball joint inspection method (TSB #01202). Since ball joints are often replaced during major suspension work, this is relevant information. Most suspension issues on these cars are related to the age and mileage-related wear of rubber components like strut rod bushings, sway bar bushings, and the strut mounts themselves. Forum discussions are filled with owners chasing down clunks that are ultimately traced to these worn rubber parts.
Buying a Used OEM Suspension Strut Assembly
For a vehicle like the LS400, where ride quality is paramount, a high-quality used OEM strut assembly can be a better choice than a cheap new aftermarket part. Lexus's original parts were built to a very high standard for durability and performance.
What to Inspect Before You Buy
- Check for Leaks: The most important check. Do not buy a strut that shows any sign of oil leakage on the main body. It should be dry and clean.
- Inspect the Top Mount: Look at the rubber on the top strut mount. It should be free of major cracks, and the metal should not be separating from the rubber.
- Examine the Coil Spring: Check the spring for heavy rust, cracks, or broken coils. The protective coating should be mostly intact.
- Look for Physical Damage: Ensure the strut body is not bent or dented, which could impede its internal function.
Mileage and Age Considerations
Suspension struts are wear items. A strut from a vehicle with 100,000 miles is likely to have significant wear. However, one from a lower-mileage (e.g., 60,000-80,000 miles) donor car can still offer many years of good service, often outperforming new, budget-tier aftermarket options. Given the age of these vehicles, finding very low-mileage used struts is rare. Set realistic expectations and prioritize struts that are clean and leak-free over ones with just a low mileage number.
Cost of Replacement (1990-1997 LS400)
| Part Type | Price Range (Per Strut) |
|---|---|
| New OEM (Lexus) | $225 - $310 |
| New Aftermarket (e.g., KYB, Gabriel) | $110 - $185 |
| Used OEM | $45 - $100 |
| Shop Labor (Per Strut) | $125 - $175 |
Replacement Overview and Torque Specs
Replacing the front struts on an LS400 is a moderately difficult job that can be done by a skilled DIYer. The rear struts are more complex due to the need to remove the rear seat to access the top mounting nuts. Buying a complete used strut assembly (strut, spring, and mount) makes the job much easier as you won't need a dangerous spring compressor.
Related Parts to Consider Replacing
While the suspension is apart, it's a perfect time to inspect and replace other worn components. On the LS400, this is especially important for eliminating clunking noises.
- Strut Rod Bushings: A very common source of clunking, especially during braking.
- Sway Bar End Links & Bushings: Inexpensive and can cause rattling or clunking noises over bumps.
- Upper Control Arms: The bushings and ball joints can wear out, causing alignment issues and noise.
Pro Tip: When replacing rear struts, use a white-out pen to mark the orientation of the top mounting studs relative to the strut body before disassembly. This ensures the new strut is aligned correctly for installation.
Critical Torque Specifications
Using a torque wrench is essential for safety and proper function. Always tighten suspension components to the manufacturer's specifications.
| Component | Torque Spec |
|---|---|
| Front Strut Top Mount Nuts (x3) | 27 ft-lbs (36 Nm) |
| Front Lower Strut Bolt | 106 ft-lbs (143 Nm) |
| Rear Strut Top Mount Nuts (x3) | 47 ft-lbs (64 Nm) |
| Rear Lower Strut Bolt | 77 ft-lbs (104 Nm) |
| Wheel Lug Nuts | 76 ft-lbs (103 Nm) |
Frequently Asked Questions (FAQ)
How do I know if my LS400 has air suspension?
The easiest way to check is to look for a switch near the gear shifter that may have settings for "High" or ride comfort modes (Sport/Normal). Also, upon starting the car, you might hear a small compressor running for a few seconds. Visually, the air struts will have rubber air bags instead of exposed metal coil springs, and small air lines connected to them.
Can I replace just one strut?
It is highly recommended to replace struts in pairs (both front or both rear) to ensure even damping and prevent handling imbalances. Replacing only one can lead to unpredictable steering, uneven braking, and accelerated wear on the new part.
Do I need a wheel alignment after replacing struts?
Yes, absolutely. Replacing a strut will always affect the vehicle's alignment angles (camber, caster, and toe). A professional alignment is required after the job is complete to ensure proper handling, prevent premature tire wear, and ensure the vehicle drives straight.
Can I convert my air suspension to these standard struts?
Yes, conversion is a popular option as original air suspension components can be extremely expensive to repair. However, it requires a specific conversion kit that includes all four strut assemblies and sometimes electronics to bypass the factory air suspension control module. You cannot simply bolt in a standard strut in place of an air strut without a proper kit.
Technical Specifications
OEM Part Numbers: 48510-50090 48510-59017 48510-59105 48510-59106 48530-59097 48131-50010 48131-50050 48131-50070 48231-50010 48231-50050 48231-50100
Fits Rear-Wheel Drive models without factory air suspension. Complete assemblies include the strut (shock absorber), coil spring, and top mount.
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.
- Lexus LS400:
- 🛍️ Shop This Part
- Symptoms of a Failing Suspension Strut
- Noises: Clunking, Popping, and Rattling
- Poor Ride Quality and Handling
- Visual Signs of Failure
- Known Issues, TSBs, and Recalls
- Buying a Used OEM Suspension Strut Assembly
- What to Inspect Before You Buy
- Mileage and Age Considerations
- Cost of Replacement (1990-1997 LS400)
- Replacement Overview and Torque Specs
- Related Parts to Consider Replacing
- Critical Torque Specifications
- Frequently Asked Questions (FAQ)
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