My 02 has made a grinding sound like you are describing for years. It is most noticeable in 3rd and 4th when I lift off throttle esp. around 30-45 mph. It goes away if I clutch in, or get back on the gas, even just slightly.
I have replaced the clutch, installed a sleeve kit for the TO bearing carrier and replaced all the transfer case bearings thinking that it would go away. At 202K miles it still does it and nothing has failed. I have run both Scotty's cocktail and Andrewtech (currently) no difference.
On that subject, don't use the Grimmspeed blend (Scotty's) as it will eventually deteriorate the shift shaft, front and rear main seals. It took 3 years, but as others discovered, the blend goes acidic. I have first hand proof of that. So far, the Andrew tech blend has been great.
Bottom line, don't worry about the noise (if it's truly the same as mine)