Did the front and rear diffs in my X5 today. Both are a pain... no drain plug in the rear and hard to access fill plug on the front. Redline 75W-110 was in there for 30k miles (previous fill was FF until 78k). Surprised how dark it was. The front was noticeably more brown in color.
Rear:

Front:

Fresh Redline 75W-110 went back in.
Rear:

Front:

Fresh Redline 75W-110 went back in.