Strut Rod and Control Arm Bushings
The strut or compression rod connects the frame and the lower control arm. It cushions and controls the arm's forward and backward movement. Worn and corroded strut rod bushings result in a clunking noise while braking. Most vehicles have positive caster for greater stability and wheel return.
Alignment angles are affected when the strut rod and control arm bushings compress and fail. Many manufacturers use a drag link like a strut rod in front of the lower control arm. It pulls on the arm instead of compressing it.
Control Arm Bushings
Control arm bushings are considered torsion bushings. This is because they allow for the twisting action needed as the control arm moves up and down over bumps in the road. Rubber bushings isolate noise from the passenger compartment. Worn bushings squeak and can typically be heard while driving.
They are rubber bonded to two thick metal plates or washers. One of these plates is attached to the frame, and the other is attached to the control arm. They cushion and help prevent vibrations from transferring to the chassis.
When worn, a clunking sound can be heard and felt more pronounced as the vehicle accelerates and disappears as the vehicle reaches cruising speeds. The vehicle may shimmy and begin to wander as alignment angles shift from this excessive looseness and play
Rear Control Arm Bushings
Inspect the control arm and track bar bushings for wear. They are typically one-piece bushings made of natural or neoprene rubber. Replace the bushing or the entire control arm, track bar, or strut rod if it has excessive wear or damage.
Solid drive axles are held in place and prevented from excess movement with control arms, strut rods, and track bars. Due to their design and small contact area on the chassis, coil spring suspension systems usually require more control arms and links than other types.
Control arms fastened to the body by a large rubber bushing and extending back to the axle ahead of the wheel are trailing control arms. Control arms that extend forward toward the axle are leading control arms.