In a motor vehicle driveline including a transfer case whose output is continually connected to a first output, a clutch, operating partially engaged, responds to a control signal to change the degree of clutch engagement, whereby a second output is connected driveably to the first output. A digital computer continually calculates a change in clutch temperature at frequent intervals and updates a running sum of clutch temperature changes. The control causes the clutch to more fully engage if the current calculated clutch temperature exceeds a predetermined reference clutch temperature.