A motor vehicle driveline that can transmit power in a 4.times.4 mode
includes two front wheels, a rear drive shaft, a differential mechanism
for transmitting power to two rear axle shafts connected driveably
through the differential to the rear driveshaft, and a clutch for
engaging and disengaging a drive connection in the differential
mechanism. A method for controlling operation of the clutch includes the
steps of operating the driveline in 4.times.4 mode, determining a current
accelerator pedal position, determining whether a current accelerator
pedal position is less than a reference position for a predetermined
period, determining a current speed of each front wheel of the vehicle,
determining whether a current speed difference between the front wheels
of the vehicle is less than a reference wheel slip for a first
predetermined period, determining during a second predetermined period
whether a current time rate of speed change of the rear drive shaft is
less than a reference rear wheel slip. The clutch is prevented from being
engaged if either the speed difference exceeds the reference speed
difference, or the time rate of speed change of the rear drive shaft is
greater than a reference rear wheel slip. Otherwise, the clutch is
engaged.