The rear suspension creates separation, IE the tires get shoved towards the ground. So as torque is applied to the ground the axle tries to spin (wheel hop, without traction bars), the caltracs turn this energy into downward pressure on the top of the spring with the triangle shaped bracket on the front spring eye. This pressure drives the tires down, away from the body, and increases traction. As a result the pinion clocks upward under hard acceleration.I don't understand what you mean when you say "separates". Do you mean separation from power/load or are you referring to suspension load separation or...? Thanks.
Here's a video I found in a quick search that illustrates what is going on. You can see even as they raise the RPM on the foot brake the back end raises. go to about the 1:00 mark or so.
To see how the pinion moves watch this video at 1/4 speed. I think this guy could use some stiffer shocks though. His bars might need to be snugged up to or something, pinion rotation seems a bit excessive.