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Unity rear conversion kit in cardboard box with label showing part number 31-513400

Unity

Unity 31-513400 Rear Conversion Kit

SKU CH-X1MA-CM6HM

Rear conversion kit replaces air suspension with passive steel springs on 1999–2006 Mercedes-Benz S-Class models excluding 4Matic

  • Converts air suspension to reliable passive steel springs
  • Fits 1999‑2006 Mercedes‑Benz S‑Class models including S320 S350 S420 S430 S500 S600
  • Excludes 4Matic variants for precise application
  • Unity Elite Suspension Line engineered for trouble‑free installation
  • Over 50 years aftermarket manufacturing expertise backing every kit

Rear Air-Spring Conversion Kit

This Unity kit replaces the rear air suspension on specific Mercedes-Benz S-Class models with passive steel springs. It fits 1999 S320, S420 and 1999-2006 S430, S500 and S600 variants. The 2006 S350 is also covered. 4Matic all-wheel-drive models are excluded from the application list.

Passive Suspension Constraints

Converting to steel springs removes the air system's ride-height adjustability and automatic load levelling. The vehicle will sit at a fixed height regardless of load. Electronic damping control, if fitted, may trigger warning lights because the air-spring sensors are no longer present.

Bolt-On Installation Notes

The kit is designed as a direct retrofit using the original mounting points, so no fabrication or welding is required. Common issues include seized air-line fittings on the old struts and the need to code out air-suspension faults in the vehicle ECU after fitting.

4Matic Exclusion Notice

Vehicles equipped with 4Matic all-wheel drive cannot use this conversion kit due to different rear suspension geometry. Buyers needing to retain air suspension or requiring adjustable ride height should not purchase this product.

Highlights

  • Converts air suspension to reliable passive steel springs
  • Fits 1999‑2006 Mercedes‑Benz S‑Class models including S320 S350 S420 S430 S500 S600
  • Excludes 4Matic variants for precise application
  • Unity Elite Suspension Line engineered for trouble‑free installation
  • Over 50 years aftermarket manufacturing expertise backing every kit

Specifications

BrandUNITY

Questions about this item

Which Unity rear conversion kit fits my 1999 Mercedes-Benz S320?

Part 31-513400 covers the 1999 S320 and S420 plus 1999-2006 S430, S500 and S600 models excluding 4Matic.

What does this kit actually replace on the car?

It retrofits steel springs in place of the factory air-ride system for a passive suspension setup.

Does the kit use the original mounting points or a different interface?

It is designed for a trouble-free installation on the listed Mercedes-Benz models using the existing suspension mounts.

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