I'm in the middle of refreshing a rear differential and just had to note how difficult the fill plug was to remove.

The diff is out of the car, so I was able to really connect with it, but wanted to reinforce when people say, remove the fill plug first before the drain plug when doing the fluid change. The plug was filled with what seemed like grout, my dental pick couldnt budge it, it had to be chiseled out. Once cleaned I pounded in a m10 allen, removed, clean, and repeat a few times. Once satisfied, I had to resort to using a 3' breaker bar to get it free. The drain plug came out without cleaning and with a 3/8s ratchet.

Now my real worry is this marring on one of the flange seals:

I thought it was me, but my tool is a 1/3 the size, and when I did the other side it popped right out and minor marring was noticed where I didnt even get close to. It almost looks like someone went over it with JB weld too? Does it make sense to do the same treatment to the other small nicks?