KYB 5550021 Suspension Shock Absorber - Rear

KYB Gas-a-Just Rear Shock for F-150

The KYB Gas-a-just 5550021 is an OE-style monotube shock absorber for the rear of select Ford F-150 trucks. It restores controlled damping for 2021-2025 Ford F-150 models with the Medium Payload Package and Off Road Suspension, without electronic suspension.

Key Features

• Monotube shock absorber construction for consistent response
• Separate hydraulic and high-pressure nitrogen gas chambers for control and ride comfort
• Rear application for 2021-2025 Ford F-150, Medium Payload Package w/ Off Road Suspension, w/o Electronic Suspension
• Compressed length: 17.13 in.; extended length: 26.77 in.; stroke length: 9.64 in.
• Upper mount type: E2(12x38); lower mount type: E2(12x38)
• Dust cover included
• KYB 5550021 direct replacement for the listed rear suspension application

Product Details

Gas-a-just is KYB’s monotube shock line for drivers who want OE replacement performance with firmer control than a conventional twin-tube design. The internal floating piston separates the hydraulic working area from the high-pressure nitrogen gas chamber, helping the shock respond quickly while maintaining a stable, comfortable ride during normal driving. For the Ford F-150, part number 5550021 is built for the rear position and matches the listed mounting dimensions and travel range.

This part cross-references Monroe Shocks & Struts (e.g., 172286) for the same application.

What It Helps Address

• Excessive rear-end bounce over bumps
• Reduced control when carrying payload or driving off road
• Loose or unsettled rear suspension feel
• Uneven damping response from a worn shock absorber
• Loss of ride stability in a rear Ford F-150 suspension service

Installation Notes

Fits 2021-2025 Ford F-150, rear, Medium Payload Package w/ Off Road Suspension, w/o Electronic Suspension. Verify compressed length, extended length, stroke length, and E2(12x38) upper and lower mounts before installation. Replace shocks in pairs on the same axle for balanced damping, and confirm the vehicle does not use electronic suspension control at the rear.

Quality Assurance

KYB manufactures the Gas-a-just line as an OE monotube replacement to restore original suspension capability. Part number 5550021 is engineered around the listed Ford F-150 rear fitment and the specified mounting and travel dimensions for accurate service replacement.