I have a 2001 ram 1500 2wd and the differential is making considerable noise. About a year ago all of the bearings inside the differential were replaced. At low speeds I can hear a sound from it that can only be described as a “wub wub wub” and a howling/whirring sound at high speeds. It’s loudest while accelerating but present at all times

 

That sounds like a brake issue. You could see if the pinion is loose and pull the cover to have a look inside, but I'd be looking at the brakes.

 

Does the noise change if you step on the brakes??

How many miles since the rebuild? Any warranty on it?