240sx Polyurethane Subframe Bushings

So, you're here because you're noticing some less-than-desirable handling characteristics in your 240SX? Maybe you're hearing some clunking from the rear end, or the car just doesn't feel as planted as it used to. Chances are, your subframe bushings are starting to give up the ghost. It's a common issue with these cars, especially as they age, and it can significantly impact your driving experience. Let's dive into what's going on and how polyurethane bushings can offer a solution.

The Worn-Out Subframe Bushing Blues

The 240SX's rear subframe is essentially a cradle that houses the rear differential and suspension components. It's bolted to the chassis with rubber bushings. These bushings are designed to isolate vibrations and road noise, providing a smoother and quieter ride. However, rubber degrades over time, especially when exposed to the elements, oil, and general wear and tear.

Here's what typically happens when your subframe bushings start to fail:

Increased Rear End Noise: You'll often hear clunking, banging, or thumping sounds coming from the rear, especially over bumps or during hard acceleration/deceleration. This is the subframe shifting around because the bushings are no longer effectively damping the movement.
Vague Handling: The car will feel less stable, especially in corners. You might experience more body roll, a wandering feeling in the rear, and generally reduced confidence in the car's handling capabilities.
Wheel Hop: During hard acceleration, especially from a standstill, you might experience wheel hop, where the tires lose traction and bounce. This is exacerbated by worn subframe bushings allowing excessive movement of the rear axle assembly.
Excessive Tire Wear: Misalignment issues caused by subframe movement can lead to uneven and accelerated tire wear.
Visual Signs: Inspect your bushings visually. Look for cracks, tears, and excessive deformation. Sometimes, the rubber will be completely separated from the metal sleeves.

Ignoring these symptoms can lead to further problems. Excessive movement of the subframe can stress other suspension components and even damage the chassis over time. That clunking noise isn't just annoying; it's a sign of underlying wear that needs to be addressed.

The Polyurethane Advantage

So, what's the solution? While you could replace the old rubber bushings with new rubber ones, many 240SX owners opt for polyurethane (poly) bushings. Here's why:

Increased Durability: Polyurethane is far more resistant to wear, tear, and degradation than rubber. This means they will last significantly longer, especially in harsh environments or with spirited driving.
Improved Handling: Poly bushings are stiffer than rubber, which reduces subframe movement and provides a more precise and responsive feel to the steering. This translates to improved cornering, better stability, and increased driver confidence.
Reduced Wheel Hop: The stiffer bushings minimize axle hop under hard acceleration.
Long-Term Cost Savings: Although poly bushings might be slightly more expensive upfront, their increased lifespan means you won't have to replace them as often as rubber bushings.

Of course, there are some trade-offs to consider:

Increased NVH (Noise, Vibration, Harshness): Because polyurethane is stiffer, it transmits more vibrations and road noise into the cabin compared to rubber. This is the most common complaint. Some people find it negligible, while others find it bothersome. It's subjective and depends on your tolerance.
Installation: Polyurethane bushings can be more challenging to install than rubber bushings. Some require specialized tools or techniques.

Ultimately, the decision of whether to go with polyurethane or rubber bushings depends on your priorities. If you prioritize performance and longevity and are willing to tolerate slightly increased NVH, then polyurethane is an excellent choice. If you prioritize ride comfort above all else, then rubber might be a better option.

Choosing the Right Polyurethane Bushings

Not all polyurethane bushings are created equal. There are different durometers (hardness) available, typically measured on the Shore A scale. Softer durometers (e.g., 70A-80A) will offer a slightly better balance of comfort and performance, while harder durometers (e.g., 85A-95A) will provide maximum performance but also transmit more NVH. It's best to research and read reviews to determine the best durometer for your driving style and preferences.

Also, ensure you purchase bushings from a reputable brand. Lower-quality polyurethane bushings can be prone to cracking or premature wear, negating the benefits of upgrading. Some popular and well-regarded brands for 240SX polyurethane bushings include:

Energy Suspension
Prothane
Whiteline

When selecting your bushings, consider purchasing a complete subframe bushing kit. These kits typically include all the necessary bushings for the rear subframe, ensuring you replace them all at once for optimal performance and handling. Replacing only some of the bushings can lead to uneven wear and stress on the remaining rubber bushings.

Installation: DIY or Professional?

Replacing the subframe bushings is a moderately challenging job that can be done at home with the right tools and experience. However, it's also a task that many people prefer to leave to a professional mechanic. Here's a breakdown of what's involved:

DIY Installation

Tools Needed:

Jack and jack stands
Wheel chocks
Socket set
Wrenches
Torque wrench
Hammer or mallet
Penetrating oil
Bushing removal tool (highly recommended – a ball joint press or similar)
Grease or lubricant (for installing the new bushings)
Safety glasses and gloves

The Process (Simplified):

Safely lift and support the vehicle.
Remove the rear wheels.
Disconnect any components attached to the subframe, such as the sway bar end links and brake lines (be careful with brake lines!).
Support the subframe with a jack.
Loosen and remove the subframe bolts. Be prepared for the subframe to drop slightly.
Carefully lower the subframe to the ground.
Remove the old bushings. This is often the most challenging part. A bushing removal tool will make the job much easier. You can also try using a hammer and chisel, but be careful not to damage the subframe.
Clean the subframe bushing bores thoroughly.
Lubricate and install the new polyurethane bushings. Some bushings may require pressing in.
Raise the subframe back into position and align the bolt holes.
Install the subframe bolts and torque them to the manufacturer's specifications.
Reconnect any components that were disconnected.
Reinstall the rear wheels.
Lower the vehicle and torque the wheel lug nuts.

Important Note: After installing new subframe bushings, it's highly recommended to get a wheel alignment. The new bushings can slightly alter the suspension geometry, and a proper alignment will ensure optimal handling and tire wear.

Professional Installation

If you're not comfortable tackling this job yourself, it's best to take it to a qualified mechanic. An experienced mechanic will have the necessary tools and expertise to perform the job safely and efficiently.

Approximate Cost: The cost of professional installation can vary depending on the shop's labor rates and the complexity of the job. As a rough estimate, expect to pay anywhere from $400 to $800 for labor, in addition to the cost of the bushings themselves.

The Bottom Line

Replacing your 240SX's worn-out subframe bushings with polyurethane bushings is a worthwhile upgrade that can significantly improve handling, reduce noise, and enhance your overall driving experience. While there are some trade-offs to consider, such as increased NVH, the benefits often outweigh the drawbacks for many 240SX enthusiasts. Whether you choose to tackle the job yourself or hire a professional, make sure you choose quality bushings and follow the proper installation procedures. With new polyurethane subframe bushings, you can restore your 240SX's handling and enjoy many more miles of spirited driving.

Drive safe and have fun!