One vehicle wheel is disconnected from a differential while the vehicle is in a front wheel drive mode. A controller checks for a malfunction of the differential while the vehicle is in the front wheel drive mode and in response to a request to enter an all wheel drive mode. If speeds of the other vehicle wheel and the differential input indicate that the malfunction is present, the all wheel drive mode is disabled and the driver is informed. If fluid temperature indicates a risk of the malfunction, all wheel drive mode is temporarily disabled and the driver is informed. If the temperature condition continues to be present for a predetermined duration, the all wheel drive mode is disabled.

Provided is a control device for a four-wheel drive which can maintain driving stability while restraining noise and vibration. A control device includes: a second control device that, when at least one of front wheel has slipped, engages a dog clutch after rotating a propeller shaft by a rotational force transmitted via first and second friction clutches; and a third control device that, if a predetermined condition is satisfied when the front wheels are not slipping, engages the dog clutch after rotating the propeller shaft by the rotational force transmitted via the first and second friction clutches. The time required to synchronize the dog clutch by the third control device is longer than that required to synchronize the dog clutch by the second control device.

A working vehicle includes a first hydraulic clutch connected to the first traveling shaft, a second hydraulic clutch connected to the first traveling shaft separately from the first hydraulic clutch, a first gear mechanism to transmit, to a second traveling shaft, power from the first hydraulic clutch when the first hydraulic clutch is engaged and not to transmit, to the second traveling shaft, power from the first hydraulic clutch when the first hydraulic clutch is disengaged, and a second gear mechanism to transmit, to the second traveling shaft, power from the second hydraulic clutch when the second hydraulic clutch is engaged and not to transmit, to the second traveling shaft, power from the second hydraulic clutch when the second hydraulic clutch is disengaged.

Even in the case where it is difficult to increase an engine torque (Te) during switching when a running is switched to a 4WD running or a 2WD running during a 2WD_d running, an alternative control section suppresses a fluctuation in the driving force of a four-wheel drive vehicle, hence it is possible to suppress a switching shock and an unnatural feeling of deceleration occurring during the switching to the 4WD running or the 2WD running.

A drive force transfer device is mounted on a four-wheel-drive vehicle having main drive wheels and auxiliary drive wheels. A cam mechanism presses a main clutch in the axial direction. An electromagnetic clutch mechanism actuates the cam mechanism and has an electromagnetic coil and a pilot clutch. When the electromagnetic coil is not energized, the pressing force of the cam mechanism, which is generated because of drag torque of the pilot clutch in the case where a output rotary member rotates faster than a input rotary member, is smaller than that generated because of drag torque of the pilot clutch in the case where the input rotary member rotates faster than the output rotary member.

A brake torque distribution system for a vehicle can include a braking system and a controller. The controller can be configured to signal a clutch of the vehicle powertrain to move to the engaged position such that the front wheels are rotationally coupled to the rear wheels and the brake torque applied to the front wheels by the braking system is transmitted to the rear wheels. The controller can be configured to signal the clutch to move to the engaged position based on an inclination angle signal received by the controller and indicative of an angle of inclination of the vehicle, a selected gear signal received by the controller that is indicative of the reverse gear ratio being selected in the powertrain, and a load signal received by the controller and indicative of a load applied to a portion of the vehicle adjacent to the rear wheels.

Methods and system are described for changing a driveline gear range from a higher gear range to a lower gear range. The driveline may include two electric machines and four clutches in a four wheel drive configuration. The methods and systems permit a driveline to change from a higher gear range to a lower gear range without stopping a vehicle.

A method for controlling a clutch unit for a drive train of a motor vehicle, wherein the clutch unit comprises a wet-running friction clutch for controllably transmitting torque from an input element to an output element of the clutch unit, wherein the clutch unit comprises oil for cooling the friction clutch, wherein heat inputs which contribute to heating the oil of the clutch unit are calculated, heat outflows which contribute to cooling the oil of the clutch unit are calculated and, as a function of the heat inputs and heat outflows, a maximum admissible clutch torque is calculated, and wherein the current clutch torque of the friction clutch is limited to the maximum admissible clutch torque.

Controlling a clutch by means of an actuator, wherein at least one first shaft can be torque-transmittingly connected to a second shaft by means of the clutch, the clutch in one of at least three states, where in an disengaged first state, a torque cannot be transmitted, in a second state, a torque can be transmitted such that the speeds of the first shaft and the second shaft are synchronized in the second state, and in an engaged third state, a required torque can be transmitted; wherein, in various states and in an operating mode associated with the particular state, the actuator is adjusted at a different speed in order to adjust the clutch.

A vehicle includes a first axle, a second axle, a driveshaft, a first clutch, a second clutch, a third clutch, and a controller. The second axle has first and second half shafts. The second axle has first and second wheels. The driveshaft is disposed between the first and second axles and is coupled to the second axle. The first clutch is configured to selectively couple the driveshaft to the first axle. The second clutch is configured to selectively couple the first wheel to the first half shaft. The third clutch is configured to selectively couple the second wheel to the second half shaft. The controller is programmed to repeatedly connect the first axle to the second axle via the driveshaft by alternating between (i) closing the second clutch and then the first clutch and (ii) closing the third clutch and then the first clutch.