Actually, the axle housing moves (rotates) and that’s what the slot is for. The spring doesn’t move, but it does get shorter with more separation and longer with under compression. The length of the spring front eye center line and the center line of the front mount of the ladder bar are two different lengths and that’s why you need the housing floater. It allows the housing to rotate to compensate for the two different arcs of the spring and ladder bar.
