KYB KG5554 Shock Absorber - Rear

KYB Gas-a-Just Rear Shock for Mercedes-Benz

The KYB Gas-a-Just KG5554 is a rear suspension shock absorber built as an OE-style monotube replacement for select Mercedes-Benz models. It is designed for drivers who want restored control, quicker response, and stable ride behavior in everyday driving and heavier-duty use.

For Mercedes-Benz 300D, 300SD, 380SEL, 420SEL, 500SEL, 560SEL, 500SEC, 560SEC, 380SE, 380SEC, 380SL, 380SLC, and 560SL rear applications, this Gas-a-Just shock uses KYB’s Gas-a-Just monotube design to separate gas and oil for consistent damping and fade-resistant operation.

Key Features

• Part number KG5554 rear shock absorber for select Mercedes-Benz applications
• Up to 25% more damping performance than original equipment shocks
• High-pressure monotube construction for immediate response and control
• Separate gas and oil chambers for fade-free operation
• Triple chrome plated piston rod helps reduce seal wear and fluid leakage
• Valving and components matched for Mercedes-Benz fitment
• Supports vehicles used for towing, heavier wheels and tires, and demanding road conditions
• Designed to work with electronic safety systems as the suspension responds as intended

Product Details

KYB Gas-a-Just shocks are built around a monotube layout with an air-free hydraulic working area and a high-pressure nitrogen gas chamber separated by a floating piston. That design improves responsiveness during normal driving while adding damping on demand when the vehicle is loaded or driven more aggressively. The KG5554 is a rear shock absorber for Mercedes-Benz models including W126 and related chassis applications, with fitment notes that exclude certain Hydromat or hydraulic suspension setups. This part cross-references Monroe Shocks & Struts (e.g., 39006) for the same application.

What It Helps Address

• Excessive rear bounce or oscillation
• Reduced steering response from worn suspension damping
• Fluid leakage caused by seal wear
• Fade during repeated suspension movement or heavier loads
• Loose rear-end control on Mercedes-Benz 300D, 300SD, 420SEL, 560SEL, and related models

Installation Notes and Tips

Fits 1976-1985 Mercedes-Benz 300D, rear; 1978-1980 Mercedes-Benz 300SD, rear; 1981-1983 Mercedes-Benz 380SEL, rear; 1981 Mercedes-Benz 380SLC, rear; 1981-1985 Mercedes-Benz 380SL, rear; 1982-1983 Mercedes-Benz 380SEC, rear; 1984-1985 Mercedes-Benz 380SE, rear; 1984-1985 Mercedes-Benz 500SEL, rear; 1984-1985 Mercedes-Benz 500SEC, rear; 1986-1991 Mercedes-Benz 420SEL, rear; 1986-1991 Mercedes-Benz 560SEL, rear; 1986-1991 Mercedes-Benz 560SEC, rear; 1986 Mercedes-Benz 560SL, rear; 1987-1989 Mercedes-Benz 560SL, rear; and 1992 Mercedes-Benz 500SEL, rear.

Follow manufacturer service procedures for rear suspension replacement, especially on models that require strut and coil spring assembly handling. Verify chassis and suspension type before installation, since some applications exclude Hydromat or hydraulic suspension systems. Compressed length is 11.06 in., extended length is 17.76 in., and stroke length is 6.69 in.

Quality Assurance

KYB is known for OE-focused suspension engineering, and the Gas-a-Just line is built to restore original vehicle capability with monotube damping technology. KG5554 is engineered for direct-fit rear replacement on listed Mercedes-Benz applications and uses a triple chrome plated piston rod to support long-term seal durability.