I searched through many old threads and could not find enough information on this awd system. This forester awd system seems to stop working at 40 mph. I can't find a problem with the system and I'm begining to wonder if it is designed to operate like this. I found several posts regarding a switch which can change this system but they seem to be more for off roading. Is this system designed to stop working at higher speeds.

What is your basis for concluding that it stops working after 40 MPH?

and we assume you have an automatic? They are 90% front 10% rear most of the time anyway. Different story on a five speed.