Spring And Damper Assembly: Notes

The spring and damper assembly are attached to cast brackets on the lower control arms and to the vehicle body by four studs secured by locking nuts. Dependant on vehicle model there are three types of coil spring and damper available:

• a standard oil passive damper (All models except supercharged),
• an adaptive damper, also known as Computer Active Technology Suspension (CATS) on 4.2L supercharged vehicles up to 2010MY, For additional information refer to Vehicle Dynamic Suspension 4.2L.
• a continuously variable adaptive damper, also known as Adaptive Dynamics System on 5.0L supercharged vehicles from 2010MY. For additional information refer to Vehicle Dynamic Suspension 5.0L.

The dampers are a monotube design with a spring located by a circlip onto the damper tube. The lower end of the damper has a spherical joint which locates in the lower control arm and is secured with a bolt.

The damper piston is connected to a damper rod which is sealed at its exit point from the damper body. The threaded outer end of the damper rod locates through a hole in the top mount. A self locking nut secures the top mount to the damper rod. The damper rod on the adaptive damper has an electrical connector on the outer end of the damper rod.

Supercharged 4.2L vehicles up to 2010MY: The damper functions by restricting the flow of hydraulic fluid through internal galleries in the damper's piston. The adaptive damper has a solenoid operated valve, which when switched allows a greater flow of hydraulic fluid through the damper's piston. This provides a softer damping characteristic from the damper. The adaptive damper defaults to a firmer setting when not activated. The solenoid is computer controlled and can switch between soft and hard damping settings depending on road wheel inputs and vehicle speed.

Supercharged 5.0L vehicles from 2010MY: The variable damper functions by adjustment of a solenoid operated variable orifice, which opens up an alternative path for oil flow within the damper. When de-energized the bypass is closed and all the oil flows through the main (firm) piston. When energized the solenoid moves an armature and control blade, which work against a spring. The control blade incorporates an orifice which slides inside a sintered housing to open up the bypass as required. In compression, oil flows from the lower portion of the damper through a hollow piston rod, a separate soft (comfort) valve, the slider housing and orifice and into the upper portion of the damper, thereby bypassing the main (firm) valve. In rebound the oil flows in the opposite direction

The damper rod is fitted with a spring aid which prevents the top mount making contact with the top of the damper body during full suspension compression and also assists with the suspension tune.

The spring rate of the coil springs can differ between models and are color coded for identification. The coil spring locates on a spring packer and a lower spring seat which is located on the damper body. The spring locates in an upper spring seat which is located on the underside of the top mount. The majority of the roll stiffness is provided by the springs rather than the stabilizer bar as this arrangement allows for a natural frequency of roll, providing a consistent suspension ride.