I drive a 2012 Tundra. Recently I heard a wah wah wah sound from under truck towards the rear. It started around 35mph really rhythmic and not so much after 50 mph. Took it to an auto shop and they said tires were good but diffrential seemed "dry" but upon further inspection he noticed my carrier bearing was bad. When he tried to move it up and down it had alot of movement. So they replaced the bearing yesterday and it feels much smoother. Even the shifter moves good(was rough when shifting from park to drive). Anyways today the wah wah wah sound was still there but got much worse and now i can feel the rhythm in the gas pedal and it starts sooner (around 25mph). No shaking or vibrating, just a loud howling wah wah sound, even when decelerating. Almost thought i heard a gritty sound too. I'm thinking a bad wheel bearing? It's just odd to me cuz once they saw the carrier bearing was bad they only focused on that. Any thoughts?
also noise didn't go away when swerving to left or right. They jacked the rear end and spun the tires but said they were good. they didn't check the front. (front tread worn on inside, didn't get them rotated yet)

 

can you include an attachement with the sound ?