2016 RAM CTD; Can’t Find Differential Service Interval!

Looks mean NOTHING. I used to do regular UOA on the rear lube and I tried brand "A" one time and it looked and smelled fine at 13300 but I started getting gear noise and the UOA showed the additives were shot. I pulled the cover and the teeth were dull gray and I know for a fact they were shiny and quiet before brand A cuz I pull the cover every change. 25k was always fine on RP lube. I went 30k once and the UOA was fine so I started changing at 30k after that. Craig