Nope.

Its hydraulically activated.

the basics of how it works is, the front wheels spin, and this builds up pressure in the front diff, which sends fluid towards the back, and locks up the clutch that is infront of the rear diff, sending power to the rear wheels.

As soon as the rear wheels are spinning the same speed as the front, the pressure equalizes, and the clutch disengages.

It could be done, but it causes premature wear on components, and it isnt as simple as hitting a switch