[DRASTiK]

I'm no rear end expert, but you're describing the same thing I went through when I had mine professionally installed. They whined some when they were breaking in. I think it's just the ring and pinion wearing the grooves in each other and when they break in, then it goes away. I'm guessing that's why you also hear cars whine in reverse often, even when they've got many miles on them. I've had my gears now for almost a year, and the only time I hear them is when I'm in reverse. Just break them in properly (my Richmond gear instructions said to drive for 10 easy miles, then let them cool for 30 minutes, and then repeat that two more times. That's all.) and the noise should go away or at least get much quieter.
Dave