I should add, if you have an early model vehicle, and the noise is all the time and getting louder as time goes on, there could be a rear axle replacement in your future.
But, I'm assuming, you have a newer model, and the problem with the lapping compound on the rear axles was on early vehicles only. (The lapping compound issue will not be present on vehicles built after August 10, 2005.)
So, if I'm assuming correctly, it is normal for a low gearing situation.