KYB KG5517 Shock Absorber - Rear

KYB Gas-a-Just Rear Shock Absorber

The KYB Gas-a-just KG5517 is a monotube rear shock absorber built for vehicles that need firmer control, quicker response, and consistent damping under load. It is a direct-fit suspension shock absorber for select Chevrolet P30, GMC P3500, Ford Mustang, Mercury Cougar, Mercury Montego, Mercury Colony Park, and Ford Thunderbird applications.

Gas-a-just uses a high-pressure monotube design with separate gas and oil chambers to reduce fade and maintain response during demanding driving. For classic rear shock replacement on a 1964-1973 Ford Mustang or 1967-1973 Mercury Cougar, the KG5517 provides a performance-oriented upgrade over a conventional twin-tube design.

Key Features

• Monotube construction with separate gas and hydraulic working chambers
• Up to 25% more damping performance than original equipment shocks
• Vehicle-specific valving and components for the listed applications
• High-pressure nitrogen gas helps maintain fade-free operation
• Triple chrome plated piston rod helps reduce seal wear and fluid leakage
• Improved steering response from higher gas pressure
• Dust cover included

Product Details

The KYB Gas-a-just line is designed for drivers who want more control from their suspension without sacrificing everyday ride quality. The KG5517 measures 10.91 inches compressed, 17.87 inches extended, and provides 6.97 inches of stroke. It uses S1 upper and lower mounts and is engineered for rear-position fitment on the listed vehicles.

This part cross-references Monroe Shocks & Struts 31069 for the same application. It is a strong match for rear suspension service on a 1985-1999 Chevrolet P30 motorhome chassis with Mor/Ryde rear suspension, a 1985-1999 GMC P3500 motorhome, and classic rear shock replacement on Ford Mustang and Mercury Cougar models.

Common Problems It Can Address

• Excessive body motion over bumps and uneven pavement
• Reduced control from worn or faded rear shocks
• Delayed steering response caused by weak damping
• Suspension fade during towing, hauling, or heavier-duty use
• Ride instability on vehicles with larger, heavier tires and wheels

Installation Notes

Verify rear fitment, mount style, and suspension notes before installation. For Chevrolet P30 and GMC P3500 motorhome applications, check the Mor/Ryde service part number and service reference U01094 to confirm the correct shock selection. On classic Ford Mustang, Mercury Cougar, Mercury Montego, Mercury Colony Park, and Ford Thunderbird applications, confirm that the rear suspension uses the listed monotube shock configuration.

Because this shock is application-specific, compare compressed length, extended length, stroke, and mount type against the original unit before installation. The dust cover is included; internal rebound spring and B-stop are not.

Quality Assurance

KYB designs the Gas-a-just line as a monotube performance shock with vehicle-specific valving and a high-pressure gas design to support consistent damping and reduced fade. The KG5517 is built for direct replacement use in the confirmed rear applications listed above.