One problem related to transmission not engage has been reported for the 1999 Subaru Outback. The most recently reported issues are listed below.
99 Subaru legacy Outback /w automatic transmission. The automatic transmission dos not engage when placed from p to d, or disengage from gear when vehicle stop. I was on a slight hill stopped. Car disengaged from gear and I could not move. In d - when I released break the carr rolled backwards causing contact with the car behind me.