Celica Reverse Sound. 2nd and 3rd Gear also help!!

I have a Toyota Celica GT and it makes this weird noise when I go in reverse. Also when I am in the lower rpms in 2nd gear and 3d gear it makes a weird scratchy sound. Almost like a sound when you sand wood with sanding paper. Any help plz I am very worried that my car will need a new Transmission :uhoh:

Have you changed the gear oil in your transmission?

I havent changed it but I did add a little

Try changing the oil and see if that makes a difference.