An 
all wheel drive system for a motor vehicle in which wheel slippage is effectively controlled and 
regenerative energy is effectively stored for subsequent utilization in the 
system. A hydraulic embodiment of the invention includes a 
hydraulic motor, a pump, a tank, an accumulator for storing pressurized fluid, and a device for 
sensing system back pressure. In response to a loss of 
system back pressure the pressure of the fluid being supplied to the motor is reduced and the motor 
discharge is directed to the accumulator, and in response to a sensed resumption of system 
back pressure regenerative energy from the accumulator is directed to the motor to assist in powering the motor. An electric embodiment of the invention includes an 
electric motor, an 
electric generator, a device for storing electrical energy such as a 
battery pack or a 
capacitor bank, a DC 
tachometer driven by the motor and operative to sense the 
motor power requirements, and a directional circuit switch 
assembly. In response to a drop in the power requirements of the motor representing wheel slippage the energy supplied to the motor is reduced; in response to a sensed overrunning condition of the motor wherein the motor is functioning as a generator the output of the generator is routed to the 
energy storage device; and in response to a sensed resumption of 
motor power requirements 
regenerative energy is directed from the 
energy storage device to the motor to assist in powering of the motor.