Also X5 4.4i has air suspension plus some X5 3.0i. The air suspension tends to fail every 75-100k. You'll noticed when your air shocks to be problem when the steering shakes, major clunking sounds too. You'll also noticed the car isn't sitting right because car will sit lower where the air shock has fail. The air pump would be working all the time too. So you would hear the air sounds as well. I would take it to mechanic because either problems would be very hard to fix.