A motor vehicle such as a four-wheel drive vehicle having a first axle shaft which is driven by a drive source and a second axle shaft which is driven by the same drive source, each of a pair of wheels associated with the second axle shaft being powered by way of individual variable torque transmitting devices, further comprising: a steering condition sensor; and a control unit which reduces a torque transmission ratio of one of the variable torque transmitting devices corresponding to the inner one of the wheels of the second axle shaft when the steering condition sensor has detected a steering angle greater than a prescribed value. Thereby, the problem of the tight turn braking can be avoided without losing the advantages of four-wheel drive. Other driving conditions such as braking and acceleration as well as an excessive temperature increase in each of the variable torque transmitting devices may be taken into consideration in carrying out the control of the variable torque transmitting devices which preferably consist of viscous couplings. Each of the viscous couplings is provided with means for externally varying the torque transmission ratio thereof and transmits torque between input and output thereof at a level which is substantially proportional to the speed difference between input and output thereof.