KYB KG5421 Shock Absorber - Rear

KYB Gas-a-Just Rear Shock for Ford Trucks

The KYB Gas-a-just KG5421 is a rear monotube shock absorber built for Ford trucks and vans that need firmer control, quicker response, and consistent damping. It is engineered for applications such as Ford F-100, F-150, F-250, F-350, and E-Series rear suspension service across the 1970-1991 model years.

Gas-a-Just Product Line

KYB Gas-a-just shocks use a monotube design with separate gas and oil chambers for fast response and fade-resistant operation. The higher gas pressure helps the shock react quickly under load, while the design supports vehicles that tow, work, or run larger tires and wheels.

• Up to 25% more damping performance than original equipment shocks
• Monotube construction for consistent control and reduced fade
• High-pressure nitrogen gas chamber for immediate response
• Triple chrome plated piston rod helps reduce seal wear
• Designed specifically for Ford truck applications
• Supports steering response and electronic safety system performance

Detailed Description

Part number KG5421 is a rear suspension shock absorber that uses KYB’s Gas-a-just monotube architecture to separate the hydraulic and gas working areas. That separation helps maintain stable damping during repeated suspension movement, which is important on Ford F-100, F-150, F-250, F-350, and E-Series rear applications where load control and ride consistency matter. The shock measures 14.37 inches compressed, 23.11 inches extended, and 8.74 inches of stroke, with lower mount type E2(12.8X38) and upper mount type S1.

This part cross-references Monroe Shocks & Struts (e.g., 34901) for the same application.

What This Shock Helps Address

• Excessive rear bounce after bumps or dips
• Reduced control when towing or carrying heavier loads
• Soft or delayed steering response from worn rear damping
• Shock fade during repeated suspension movement
• Uneven ride quality on older Ford truck and van suspensions

Installation Notes and Fitment

Fits 1970-1976 Ford F-100, rear. Fits 1976-1979 Ford F-150, rear. Fits 1977-1979 Ford F-250, rear, from serial no. Y20001. Fits 1979 Ford F-350, rear. Fits 1975-1991 Ford E-250 Econoline, rear. Fits 1975-1991 Ford E-250 Econoline Club Wagon, rear. Fits 1975-1991 Ford E-350 Econoline, rear, excluding motorhome chassis. Fits 1977-1991 Ford E-350 Econoline Club Wagon, rear, excluding motorhome chassis.

Verify mount style, compressed length, and extended length before installation. This rear shock includes a dust cover and uses an R-stop configuration. Match the vehicle’s suspension setup and confirm clearance for the monotube body during full suspension travel.

Quality Assurance

KYB designs Gas-a-just shocks for performance-oriented OE replacement use, with valving and components tailored to Ford truck and van applications. The monotube design is intended to maintain damping consistency and reduce aeration-related fade in demanding rear suspension service.