Unity 31-513400 Rear Conversion Kit
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.
How it compares
Measured against everything we stock in Brake Service Tools & Presses, at today’s prices. Recalculated every night.
- Price $447.99
- Pricier than about 92% of the 1,702 comparable items (median $86.99).
Specifications
| Product | |
|---|---|
| Brand name | UNITY |
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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