Agree with above, (98% front wheel drive normally). If ABS sensors detect front wheel slip, computer operates a solenoid to engage the rear drive. This is automatic. (And an improvement over the old viscous coupling system used on the old model) You can manually force engagement of 4x4 at speeds below 50km/hr (31 mph) by (on the 4x4) pressing the ELD button, or (on the Cross), turning the dial to the off road setting. This also allows the ABS sensors to act to provide 'electronic diff lock' if a rear wheel spins -- note that in this sense 4x4 and Cross are identical in the way they operate - the 'auto setting' on the Cross dial is what the 'normal' 4x4 defaults to anyway (But the Cross can also then bring in hill descent control with a second turn of the dial)