You realize that's how the automatic transmissions work now, right? Instead of a split diff, there's a second gear set in the trans. A "6 speed" isn't 6 separate forward gears, is a 3 speed auto in front of an overdrive unit that combines 3 gears with 2 for six total. It's a manual trans and a split axle all combined into a single unit. It's been like this since 2003 when the 5R110W came out; there are six total gear combinations but only 5 are used.