Tesla Motors Club

At the risk of sounding like just another loon with an idea on the internet, I was thinking that if you implemented a 4WD system with different final gear ratios in the front and back, it could effectively operate like a 2-speed transmission. At low speeds, all four wheels will drive the vehicle, but with more acceleration coming from the wheels with the lower drive ratio. At higher speeds those wheels could free-wheel using a clutch or whatnot, leaving the high drive-ratio wheels to continue accelerating the car in 2WD mode.

In this manner, you can preserve low-end acceleration while adding a higher top speed.