2nd Gen A4WD Question

[cosermann]

Seems like I've read someplace that the A4WD mode is vacuum actuated.

Two Questions:

1. Is this correct?
2. If so, if one loses vacuum, does the system default to 2WD or A4WD?

 

[cosermann]

To put a finer point on it, IIRC, in 2H mode, a vacuum is used by the IWE system to disengage the front driveline at the wheel ends and send all available engine torque to the rear wheel.

So, my thinking is, if that vacuum fails for some reason, when the front driveline is being dragged along for the ride (decreasing MPG among other things). Is this correct?