electric differential?

[dcb]

So maybe I'm learning enough to be dangerous, but it looks like if one wanted to do the "dual DC" motors w/serial parallel trick like the zilla controller supports (and as used in white zombie and killacycle to good effect), what happens if you hook one motor up to each driveshaft (i.e. simple chain reduction) so that the 2 motors are only connected through the ground?

Do you get a quasi-posi effect? Like the one motor starts spinning a wheel and draws less current so more current is available for the non-spinning wheel and motor? Or what would happen there?