is this a differential or bearing problem...

[caseyjj1]

When I drive around at 35mph I hear a whining vacuum noise coming from the back. It goes away after 40. But when I'm driving at highways speeds and go back down to 35 it is even louder. I have a 2002 V6.

 

[whododat1]

Do a search on it and you will find your answer.
But yes there is sometimes a problem with rear differentials
which is why I am switching to Amsoil 75W-140 severe gear.