So if you rev it up in neutral it doesn't make the noise at all?
It could be a lot of things, but at least we can narrow it down based off of making the noise when in gear or not. Some items have bearings and are spinning all the time regardless whether in gear or not. Other items just in gear. So we can start narrowing that down. Your carrier bearing (item E) is just a small bearing inside that housing. On the other side of that is your output shaft bearing. The carrier bearing can be replaced just by pulling that housing off. However, if it is your output shaft bearing that will require you to split the cases.
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