Toyota Repair: Loud humming noise from rear, auto salvage yards, wheel bearing

Question
I bought a used 1994 Toyota Sienna and now there is a very loud humming sound coming from the rear like an airplane sound.  I have replaced a wheel bearing but it is still there.  Will you please help me in identifying what is it that I needed to fix or replace?

Thank you.

Answer
You have replaced one wheel bearing, it's possible that it may be the other side making noise or the differntial bearings, did you not drive this vehicle before buying it? I would recommend replacing the other side bearing and if that doesn't fix it you are looking at replacing the differential assembly, there are used ones available at most auto salvage yards at reasonable cost.