If you own a Lexus GS400 from the first generation (1998–2000), you know it delivers a smooth ride and solid handling. But over time, the rear suspension components wear out. Whether you're chasing a clunking noise, sagging rear end, or uneven tire wear, understanding the parts that make up the rear suspension is essential for a proper repair or upgrade. This guide covers the key rear suspension parts for the Lexus GS400, what to look for when buying replacements, and how to choose between OEM and aftermarket options.
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Main Components of the Rear Suspension
The Lexus GS400 uses a multi-link rear suspension design, which offers a good balance of comfort and performance. The main components include control arms, bushings, shocks, coil springs, and stabilizer bars. Each part plays a specific role in maintaining alignment, absorbing bumps, and keeping the rear tires planted.
Control Arms and Bushings
The rear suspension has several control arms: upper and lower control arms, plus toe links and camber arms. These arms connect the rear subframe to the wheel hub and control the wheel's motion. Over time, the rubber bushings at the pivot points crack and degrade, leading to loose handling and alignment issues. When replacing control arms, it's common to replace the entire arm with pre-installed bushings, or press in new bushings if the arm is still solid. For the GS400, the lower control arms and toe links often wear first.
Shocks and Struts
The GS400 uses separate rear shocks (not struts). The shock absorber controls rebound and compression damping. Worn shocks cause a bouncy ride, poor handling, and longer stopping distances. For the rear, you'll need to replace the shock assembly, which includes the shock absorber and sometimes the upper mount. Many owners upgrade to gas-charged shocks like KYB Excel-G or Bilstein for improved control.
Coil Springs and Air Suspension
The standard GS400 came with coil springs. However, some models (especially with the optional air suspension) have rear air springs. Coil springs rarely need replacement unless they sag or break. Air springs can leak or fail over time, causing the rear to sit low. Converting air suspension to coil springs is a popular and cost-effective option. If you keep air, use OEM or high-quality aftermarket air springs from Arnott.
Stabilizer Bar and Links
The rear stabilizer bar reduces body roll during cornering. It connects to the suspension via end links. Worn end links cause a clunking noise over bumps. The stabilizer bar itself is durable but the bushings may squeak. Replacing the end links and bushings is a straightforward fix.
Signs Your Rear Suspension Needs Replacement
Recognizing the symptoms early can prevent uneven tire wear and safety issues. Common signs include:
- Clunking or rattling from the rear when going over bumps (often worn control arm bushings or end links).
- Excessive bouncing after hitting a bump (worn shocks).
- Sagging rear or the car sits lower on one side (broken coil spring or leaking air spring).
- Uneven tire wear on the rear tires (alignment issues due to worn control arms).
- Drifting or wandering at highway speeds (loose suspension components).
If you notice any of these, inspect the components. A visual check can reveal cracked bushings, leaking shocks, or bent arms.
OEM vs Aftermarket Parts
When buying rear suspension parts for your Lexus GS400, you have two main choices: OEM (Lexus/Toyota) or aftermarket. OEM parts are exact replacements, but they are more expensive. Aftermarket parts offer a range of quality levels, from budget-friendly to high-performance upgrades.
- OEM: Best for factory ride quality and longevity. Ideal if you plan to keep the car stock. But expect to pay a premium.
- Aftermarket: Brands like Moog, KYB, Monroe, and TRQ offer quality parts at lower prices. Moog is known for durable bushings with grease fittings. KYB and Bilstein excel in shocks. For control arms, consider Detroit Axle or TRQ if you need a full set.
Avoid no-name brands. Cheap parts often fail quickly and can cause alignment issues. Stick with reputable manufacturers.
Important Considerations for the GS400
The GS400 came in both rear-wheel drive (RWD) and all-wheel drive (AWD) versions. RWD is more common. The AWD version uses a different rear subframe and some unique components. Always verify your specific model year (1998, 1999, or 2000) and drive type before ordering.
Also, the GS400 uses a double-wishbone front suspension, but the rear is multi-link with separate subframe. Some parts, like the toe links, are specific to the GS400 and not shared with the GS300. Check fitment carefully.
If you're lowering the car, you'll need shorter shocks and springs. For a mild drop (1–1.5 inches), coilover kits from BC Racing or Tein are available but more expensive. Alternatively, use Eibach or H&R springs with KYB shocks for a budget-friendly upgrade.
Recommended Parts and Brands
Based on common replacement needs, here are specific part recommendations:
- Rear Shocks: KYB Excel-G (part #343514 for LH, #343515 for RH) or Bilstein B6 (part #24-305115 for LH, #24-305116 for RH).
- Rear Coil Springs: Moog (part #81116) or Eibach Pro-Kit (part #4586.140) for a 0.8-inch drop.
- Rear Lower Control Arms: Moog (part #RK621166) with polyurethane bushings.
- Rear Toe Links: Moog (part #RK621167) or Dorman (part #522-221).
- Rear Stabilizer End Links: Moog (part #K750215) or TRQ (part #BSA63225).
- Rear Shock Mounts: Replace with OEM Lexus (part #48531-50020) or aftermarket like Westar (part #EM-2410).
For air suspension conversion kits (if you have air ride), Arnott offers complete coil spring conversion kits (part #AS-2705).
Final Recommendation
Start by diagnosing exactly which parts are worn. A shop can perform a suspension inspection for peace of mind. For most owners, replacing the rear shocks, lower control arms with bushings, and stabilizer end links will restore the factory ride quality. If your car has air suspension and you want reliability, convert to coil springs using a kit from Arnott.
Stick to OEM for bushings and mounts if you want maximum longevity, but premium aftermarket (Moog, KYB) is perfectly fine for most needs. Always replace parts in pairs (both sides) to maintain balance. With the right components, your Lexus GS400 will ride and handle like new again.