The rear differential on my 2005 X5 with 230,000 miles has decided to pack it in and as a result I’m left trying to find a replacement.I’m definitely not going to be forking out for a new one.So I have searched for a used replacement with the 3.91 ratio.My problem is that these seem to be very scarce now.My other option is to replace both the rear and front diff with a 3.73 version which I can get relatively easily.Has anybody out there done this or does anybody see any potential problems with this?Thank you for any help in advance.