Originally Posted by snuffer
Or maybe the panhard rod helps.
Sure it does, just as the a-arm in the rear helps prevent lateral movement along the axis of the axle. I would suggest the panhard rod's primary purpose is to prevent lateral movement of the axle.
Everything is clearly performing more than one function, but I dont think Texas D was looking for a force diagram of the suspension, I think he wanted to know what would happen if the trailing arms weren't present.