I could've sworn the Hummer was 2 wheel drive and shaft driven.
It was on tactical to practical on the discovery channel. He spunt he cranks while holding the bike and both wheels spun simultaneously.
http://www.popsci.com/popsci/auto/ar...447792,00.html
There is an article I found, though. But, yeah, that Hummer bike may not be 2 wheel drive. I could've sworn it, though.