1997 subaru imprezza 2.2 automatic AWD wagon, bought used, suspected last winter the AWD did not work. Just jacked up rear wheels with car transmission in park, and could spin either rear wheel with no effort. Noticed the drive shaft leading to the transmission was also turning, so assume the rear differential is ok. I thougth I would not be able to spin the rear wheel. Is there a center differential on the car? Is it part of the transmission? Could there be a driveshaft pin sheared or splines stripped (if splined)?

There is a central diff(called a TORSEN diff)and yes it has splines on the output shaft.NOW this IS a front wheel drive car that goes into 4wd when traction to the front is compromised(slipping)they are not allowed to call it "quattro"or 4wd as its NOT.jack up the rear and block the front wheels,start the engine and put it into gear,the rear wheels should turn if the central diff is operating correctly.if not the best solution is to get a diagnostic done at a subaru dealer(you can then decide if you are capable of fixing it yourself or are willing for them to fix it)It is not as simple a system as some people would make out as you have electronics to control the front/rear traction.and the diagnostic computer they use is invaluable.AND EXPENSIVE.