Our 98 Outback Limited is having some issues with the AWD. Rear wheels will spin on the snow and ice and front wheels have no power! What on earth could be causing this? This is an occasional problem as it does work properly but is more recently having issues. Again, the rear wheels do have power and spin while the front have no power. When it does this the fronts will suddenly grab as the engine is reved and make clunk noise. Someone please help.