KYB 5540004 Suspension Shock Absorber - Rear

KYB Gas-a-Just Rear Shock for Lexus IS

The KYB Gas-a-Just 5540004 is a monotube rear shock absorber built as an OE-style replacement for select Lexus IS models. It is engineered to restore original handling response while adding the firmer control expected from a high-pressure monotube design.

Compatible with 2014-2021 Lexus IS250, IS350, IS200t, and IS300 rear suspension applications, this KYB Gas-a-Just shock is a direct-fit solution for drivers replacing worn OE dampers on a Lexus IS250 or Lexus IS350 RWD platform.

Key Features

• Monotube OE replacement design for rear suspension service
• Separate hydraulic and nitrogen gas chambers for responsive damping and consistent control
• High-pressure gas charge helps reduce fade during repeated suspension movement
• Triple chrome plated piston rod helps reduce seal wear and fluid leakage risk
• Internal rebound spring included for controlled extension
• Built for vehicles that tow, carry load, or run larger wheels and tires
• Supports steering response and electronic safety system performance by maintaining suspension control

Product Details

The Gas-a-Just line from KYB focuses on monotube shock absorber construction for drivers who want OE replacement fitment with firmer response. This design uses an air-free hydraulic working area for control and a separate high-pressure nitrogen chamber with a floating piston to maintain consistent damping. The result is a rear shock that reacts quickly to road inputs while maintaining a comfortable ride in normal driving.

Part number 5540004 is specified with a compressed length of 18.5 inches, extended length of 24.05 inches, and stroke length of 5.55 inches. Mounting details include an E2 lower mount and an S1 upper mount. This part cross-references Lexus OE numbers 4853080665 and 4853080666 for the same application.

Common Issues This Shock Can Address

• Rear suspension bounce or poor damping control
• Excessive body movement during braking, cornering, or lane changes
• Reduced steering response from worn rear shocks
• Fluid leakage from aging shock absorbers
• Loss of ride control on vehicles with heavier wheels or added load

Installation Notes

Fits 2016-2021 Lexus IS300, rear. Fits 2014-2020 Lexus IS350, rear. Fits 2017 Lexus IS200t, rear. Fits 2016 Lexus IS200t, rear. Fits 2014-2015 Lexus IS250, rear.

Additional components, dust cover, or bushings may be required depending on the vehicle and existing suspension condition. Verify mount style and dimensions before installation, and inspect related suspension hardware for wear before replacing the shock.

Quality Assurance

KYB is a major OE suspension supplier, and the Gas-a-Just line is built to restore factory-style control with monotube performance characteristics. Part number 5540004 is engineered for consistent damping response and durable service in rear suspension applications.