2017 rear differential noise

New member here, so bear with me... I have a 17 (Wife's) and 16 tundra. 17 rear diff scrapping sound --- rotor (OEM rotor) grinding against e brake back plate.... no obvious rust, diff gear oil looked fine, no play i could feel, and no grinding sound when truck is in drive on the lift.... but spin axle by hand n hear a clear gear tapping sound (poor explanation, but have video .. too big for upload)... dealer states limited slip on tundra is reason for sound.. no issue!! My issue is my 16 has 20k more miles n sound is very different! Thanks for any insight

 

FYI, I don't think Tundra has a true limited-slip. Rear diff is an open diff but brake assisted to kind of simulate limited slip behaviour ... I think it's called Auto-LS. Tundra rear diff is very solid!

Any chance it's wheel bearing noise. Or brake sticking a little or calipers or warped rotor. some say Tundra rotors are not the best. I don't have any issues with my '16 ... Do you drive in deep water a lot?