Abstract: A motor vehicle comprises two driven axles, one of which is adapted to be driven by a drive train, which comprises a liquid friction coupling, which is preceded in said drive train by a clutch, which is adapted in a first position to cause the rear axle to be driven via said liquid friction coupling, in a second position to by-pass said liquid friction coupling and in a third position to disconnect said rear axle from said drive train. In a motor vehicle comprising a transmission comprising at least one cross-country or crawling gear the clutch is adapted to assume said second position under the control of a pick-up, which is associated with the cross-country gear or gears, a switching and control stage, and an actuator in response to the selection of the cross-country gear or one of the cross-country gears. That actuation is independent of the position previously assumed by the clutch. The clutch will remain in that position until a road gear is selected in the transmission.

Abstract: A differential gear and control system for motor vehicles having a single driven axle and at least one undriven axle comprises a differential gear and a differential lock, which is adapted to be controlled in dependence on the speed of travel of the vehicle. In order to increase the traction when the vehicle is started whereas the handling of the vehicle should not adversely be affected by a locking of the differential gear, the differential lock is adapted to be controlled so that it exerts on the differential gear a restraining torque which decreases as the speed of travel of the vehicle increases from zero to a predetermined speed of travel.

Abstract: A motor vehicle comprises two driven axles, one of which is adapted to be disconnected from the drive member by a disconnecting clutch, which is adapted to be automatically disengaged by clutch control in response to a brake application. In order to decrease the structural expenditure whereas the reliability of the handling of the vehicle is not adversely affected the disconnecting clutch consists of a positive clutch, which when it has been disengaged in response to a brake application is adapted to be automatically re-engaged in response to a release of the brake pedal or an actuation of an accelerator pedal when the engine is running at a speed above a predetermined threshold.

Abstract: In the operation of a drive system for a motor vehicle comprising means for permanently driving a first pair of wheels and automatically operable means for selectively driving a second pair of wheels in dependence on the slip of the first pair of wheels, a frequent change between a four-wheel drive mode and a two-wheel drive mode for measuring purposes and for speed compariosn should not be required and this should be achieved with structurally simple means. To that end two sensors are respectively associated with the two permanently driven wheels and are operable to generate speed signals representing the speeds of said two wheels and to deliver said signals to a computer, which derives an actual speed difference signal from said speed signals and in which respective characteristic speed differences, which are specific to the vehicle, are stored for the two-wheel drive mode and for the four-wheel drive mode.

Abstract: A motor vehicle comprises a primary driven axle and a secondary driven axle which is adapted to be arbitrarily driven under the control of an electric control device. In order to ensure a more reliable handling of the vehicle during a braking, the electric control device comprises a switch, which is arranged to be automatically enabled in response to a rise of the speed of travel of the vehicle to a predetermined value and which in an enabled state is arranged to respond to a braking operation or a predetermined braking operation by a disabling of the drive train leading to the secondary driven axle and to maintain the drive train disabled, and an additional switch, which is manually operable to enable the drive train.

Abstract: A four-wheel drive of a motor vehicle is arranged to effect automatic changes between a two-wheel drive mode and a four-wheel drive mode in dependence on the slip of two wheels (5) which are permanently driven. A frequent change from the four-wheel drive mode to the two-wheel drive mode for a speed comparison is to be avoided in a four-wheel drive which has a relatively simple structure. Two sensors (12) are associated with the two permanently driven wheels (5) and the output signals of said sensors are delivered to a computer (11), which determines for consecutive units of time the occurrences of the speed difference between said two wheels in excess of a predetermined threshold value and generates a distribution curve of said occurrences in consecutive units of time. That distribution curve is compared in the computer with a corresponding stored limiting curve, which is applicable to a minimum coefficient of road friction.

Abstract: A motor vehicle comprises at least two driven axles (2, 5). One (5) of said axles can be disconnected from the prime mover (1). In order to prevent a swerving of the vehicle without a need for interrupting the transmission of power to one (5) of the driven axles (2, 5) during each braking operation, the vehicle is provided with a sensor (6) for measuring the angular acceleration of its yawing movement. In response to a rise of the angular acceleration to a predetermined value the sensor (8) causes a clutch control means (15) to disconnect one driven axle (5) from the prime mover (1), or operates means for effecting a pressure drop in the brake system.