Re: How quick can Quadra drive react?
Quadra drive has a progressive coupling in the T-case, which progressively can transfer the torque to the front wheels, as soon as a speed difference occurs between front and rear propeller shafts. This speed difference is important, because that drives the pump to activate the clutch pack of the progressive coupler. How quick this works i can't tell you. (this part is the same for Quadra Trac II.)
Quadra drive has then also vari-loks in the differentials, which functions almost the same as the progressive coupler in the T-case. But in this case it works on the speed difference of the two wheels on the same axle.
So as soon as a speed difference is there, the pump output will activate the clutch and both wheels on that axle will be fixed together.