O1m Differential Fluid?

Has anyone ever changed there differential fluid or ever checked it? Im about to hit 30k since my new transmission has been installed and im going to change the fluid and filter but cant help to think if i should suction out the old differential fluid and add new stuff.

The diff fluid (gear oil) usually looks clean even around 100k.. I'd do just the ATF for now.. Maybe pull the speed sensor and see what the fluid looks like and go from there..

I do mine at the same time ATF around 50k.

Didn't help in original FDB(60k) or the VW reman FDB(155k) both had diff failures really without notice.

Looked clean but I changed it anyways using my Pella.

I'm gonna try an additive this time too since I have a locally reman FDB to be installed now in a different car.