Well please keep this post updated at any point if you figure it out! I’m at 170k miles myself, we could be having the same problem. I have just ordered the ring and pinion,and all bearings. Everything just short of a new differential carrier. May as well do everything if I’m going to do it...
Mine is making the same whir whir whir noise when slowing down, and grinding when going faster. It’s definitely coming from the rear end from what I can tell. Also, whenever I go to slow down or I’m coasting with my foot off the gas, at around 30 or lower sometimes you hear a light tap tap tap...