KYB 5540018 Shock Absorber - Rear

KYB Gas-a-just Rear Shock for Super Duty

The KYB Gas-a-just 5540018 is a rear monotube shock absorber built for Ford Super Duty trucks that work, tow, and carry heavier wheel and tire setups. It delivers quicker response than a conventional twin-tube design and helps maintain consistent control under load.

Key Features

• Provides up to 25% more damping performance than original equipment shocks
• Engineered for Ford Super Duty truck applications
• Monotube design adds damping for trucks that tow, haul, and run larger tires and wheels
• High-pressure gas and oil separation supports fade-free operation and fast response
• Triple chrome plated piston rod helps reduce seal wear and fluid leakage
• Higher gas pressure improves steering response and chassis control
• Supports proper suspension behavior for vehicles equipped with electronic safety systems

Product Details

KYB Gas-a-just shocks use two working chambers: an air-free hydraulic section for control and a high-pressure nitrogen gas section with a floating piston for ride comfort and immediate performance when conditions change. This design is well suited to 2017-2020 Ford F-250 Super Duty rear shock replacement and 2017-2020 Ford F-350 Super Duty rear shock replacement, as well as 2021-2022 Ford F-350 Super Duty rear shock replacement. Part number 5540018 is also a direct reference point for shoppers comparing OE-style replacement options for these trucks.

This part cross-references Ford HC3Z18125AB and HC3Z18125EB for the same application.

What It Helps Address

• Excessive bounce or rear-end instability over rough pavement
• Reduced control when towing or carrying heavy loads
• Shock fade from heat and aeration during demanding use
• Delayed response after steering or lane changes
• Wear related to fluid leakage at the piston rod seal area

Installation Notes and Tips

Fits 2017-2020 Ford F-250 Super Duty, rear. Fits 2017-2020 Ford F-350 Super Duty, rear. Fits 2021-2022 Ford F-350 Super Duty, rear. Verify rear suspension configuration and compare the original shock length, mounting style, and part number before installation. After replacement, inspect related suspension components and confirm proper ride height and road test behavior.

Quality Assurance

KYB designs the Gas-a-just line as a monotube performance upgrade for demanding truck use, with valving and components tailored to Super Duty Ford applications. Part number 5540018 is built to support consistent damping response and stable operation in the rear suspension.