Many stock vehicles came from the factory with coil-spring suspensions. If you look closely at the links that attach the axle to the chassis, you wont see the spherical rod-ends like those used on many off-road vehicles. Instead, what you see is a simple bushing, like on a leaf-spring. The bushing has the ability to pivot, which will allow straight up and down axle movement, but it does have much ability to rotate/twist. Is it the rotating/twisting action of a spherical rod-end that allows a rock-crawler axle to articulate the way it does??? Lets face it, a stock vehicles can articulate to a point, but a "purpose-built" rock buggy can have insane amount of articulation! Is it the spherical rod-ends that allow for so much of this articulation????