[Spridgets] Diffs again, if I may

[derf]

Go here:
http://en.wikipedia.org/wiki/Differential_(mechanics)
Look at the top right picture.  Your Phantom grip applies pressure to the
green gears in the pic, discouraging their rotation.  This, in turn, makes
the wheels want to turn at the same rate.  If one wheel comes off the
ground, the power going to the wheel still on the ground is then determined
by the amount of force that your Phantom applies.  The Phantom makes it
harder for the planetary gears in a diff to turn.  If you lock those
planetary gears, you have a spool or full positive traction.
It helps to first understand how a standard diff works and then see the
effect of the Phantom.
Cheers,
Derf