IIRC the AWD versions (recognizable by a 'D' at the end of the model name, as in P90D) use 2 motors, one for the front and one for the rear. These two motors ha

IIRC the AWD versions (recognizable by a 'D' at the end of the model name, as in P90D) use 2 motors, one for the front and one for the rear. These two motors have different gear ratios, so one is more opimized for torque and the other for high speed. The rear wheel drive versions have a single ratio which has to strike a balance between speed and torque. This is also the reason that the AWD versions are faster than the RWD even though they are heavier due to the additional motors.