Hydrostatic power transmission at the wheels?
Can the concept of a screw air compressor be reversed to transmit drive to the wheels?
Engine can be used to run a compressor, a highly compressible gas like nitrogen maybe used.....
Compressed gas to be stored into a tank.
Out put valve to feed compressed gas to "reversed air compressors" at wheels,drive can be adjusted by controlling this valve .
Engine starts at a minimum pressure at storage tank and stops at max pressure.
this is what i had in my mind,some benefits of this concept is maximum fuel efficiency due to constant rpm of engine,takes out the weight of gearbox,propeller shaft and differential unit.