This is late, but in case of searchs for it, the inventor was Vernon
Gleasman back in 1950s, his company made them until the 80s when they
sold the Patents to Gleason Works when the Hummer contract was to much
for production. As the the tracked vehicle steer drive, thats still
around and has been improved. Look at Torvec Inc. the company Vernon
later founded, they are working on the next Gen. Torsen and the FTV
which uses the steer drive. Website www.torvec.com