Trunnion - Free Movement Suspension
The trunnion can be found where the upper or lower control arm attaches to the spindle. The trunnion was used on older vehicles such as the AMC Rambler, Hudson Jet, and Willys passenger cars.
This part was attached to the upper control arm with steel threaded bushings. The center of the trunnion has a bronze bushing in the center, which slides onto the shaft of the spindle, bearing first, and then is attached with a castellated nut.
The trunnion allows the spindle to rotate when the vehicle is steering, and allows for up-down movement of the control arms at the same time. Trunnion assemblies have been phased out in favor of upper/lower ball joints.