Years ago when I worked for car dealers in the 80’s.
When we heard a whine or noise the car manager would give us a banana peel to ad to the diff. It would grind it up and the fibers would quiet the noise for sometimes years.... lol! I know not the proper way to fix BUT your post brought back a memory from the past. Lol!
Honestly it is hard for us to determine what noise you have just by a single post. gears could had some rust or bearing are bad. So many issues to work around. The only way to properly diagnose and fix is take it apart and figure it out.
Syleng1
