Rear End gear Whine

When I got my 8 1/4 back from DTS after it was rebuilt with a new suregrip and 3.91's it had a little whine, was told its normal. That was in 1997 and it must have well over 50,000 miles by now, if not much more. Think its better now but maybe I don't notice it anymore ? DTS told me HP gears have a little whine to them