Lately I have been hearing sound when I'm driving it. Like a howling or gurgling noise that isn't so loud when I accelerate past 45 in my Subaru 2015 crosstrek. Is it possibly the differential gear oil needs changed.or a bad differential. I didn't realize that gear 0il needs changed every 30,000 miles. I know it not the wheel bearings too. It's either coming from rear or front we are not sure. We were gonna take it somewhere to change the gear oil if that makes a difference.