itix, below are couple of simple images I sketched, to give you an idea how an asymmetrical diff can physically look. Most asymmetric diffs actually do not use this arrangement, but this is a simple way of representing an asymmetric diff and should you decide to use such simple design in your vehicle, it will still perform such function.
So here it is starting with an image of symmetric diff for reference:
http://www.geocities.ws/rallytech/me...ymmetric_1.jpg
And the asymmetric one:
http://www.geocities.ws/rallytech/me...ymmetric_2.jpg
You can see how in the asymmetric diff, one of the side gears is smaller than the other which would result in smaller torque being applied to the shaft connected to that side gear.