Hopefully the CPO will cover!
Let us know what it turns out to be.
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Listening to that sound, I would be thinking ring gear. I say that as my experience with CV joints is that they acts quite the opposite of what you are experiencing (ie, lots of noise under load, no/low noise when coasting). Also, listening to the noise, it is a heavy metal "thud", not a whirring sound. I don't think it is anything on the rim contacting the caliper as this would happen all the time or go away as the wheel spins faster due to centrifical force. So, this takes me back to the differential. There is a little bit of movement that is allowed on the ring pinion and that would put it touching one surface under load and touching a different surface when coasting/reversing. With his being said, if you were to get into a parking lot, you should be able to accelerate in reverse with the noise always there and when you ease off the gas, the noise should go away. this to me would confirm the ring gear has a chipped/missing tooth.