330 Ci gear whine

I have a 2001 330Ci with 30,000 miles. I hear a slight rear end gear whine
under light load. It doesn't seem excessive yet; but, I thought it unusal
for the milage. Does anyone else have this and could it be considered
normal. The nearest dealer is like 100 miles away; and, I hate to make the
drive just for that. (I'm one of these people that, most of the time,
prefers to listen to the car, instead of music; and, I probably hear too
much.)