KYB 553603 Shock Absorber - Rear

KYB Gas-a-just Rear Shock for Cadillac CTS

The KYB Gas-a-just 553603 is a rear suspension shock absorber built as an OE-style monotube replacement for the 2003-2007 Cadillac CTS with FE1 suspension. It is engineered to restore original control and handling while adding quick response for heavier-duty driving conditions.

Gas-a-just Product Line

KYB Gas-a-just shocks use a monotube design with separate hydraulic and high-pressure nitrogen gas chambers. That layout supports responsive damping for normal street use and firmer control when the suspension is working harder, such as during towing, hauling, or when larger wheels and tires are installed.

Key Features

• OE monotube replacement for rear suspension service
• Fits 2003-2007 Cadillac CTS, rear, with FE1 suspension
• High-pressure monotube construction separates gas and oil for consistent damping
• Triple chrome plated piston rod helps reduce seal wear
• Dust cover included
• B-stop and R-stop included in the design
• Part number 553603 for direct catalog lookup

Detailed Description

KYB 553603 is designed for drivers who want to restore the factory feel of the Cadillac CTS rear suspension without changing the vehicle’s intended behavior. The monotube shock uses an air-free hydraulic working area for control and a separate nitrogen gas chamber with a floating piston for fast response and stable operation. This design helps maintain damping consistency and supports steering response when the suspension is under load. The rear shock absorber measures 18.54 inches compressed, 22.54 inches extended, and provides 4.00 inches of stroke.

This part cross-references Monroe Shocks & Struts (e.g., 5788) for the same application.

What It Helps Address

• Excessive rear bounce or oscillation
• Reduced handling control in the Cadillac CTS rear suspension
• Shock fade during repeated suspension movement
• Seal wear related to fluid leakage
• Loss of steering response from worn rear dampers

Installation Notes

Compatible With 2003-2007 Cadillac CTS, rear, FE1 suspension. Verify upper and lower mount types before installation: upper mount type S1 and lower mount type SPECIAL. Confirm compressed length, extended length, and stroke against the original shock before replacement. Part number 553603 should be matched to the vehicle’s suspension code and rear position during ordering.

Quality Assurance

KYB designs Gas-a-just shocks as OE replacement components for restoring factory suspension performance. The monotube layout, high-pressure gas charge, and chrome piston rod construction are used to support consistent damping and long-term service in daily driving conditions.