31003

this is on the drivers side of the front differential, after pulling out the axle shaft

(1999 Silverado 1500 4WD 5.3) I am changing the driver side front axle bearing because there was a lot of play in the shaft right there, and it was also leaking. There is also a loud whirring gear noise, noticeable when driving from 20 to 40 mph, coming from somewhere up front. I have the shaft and seal out. This is a picture of the spot the shaft came out, after removing the seal. 1. What is that piece I highlighted with a black circle? 2. What is the circular area around the outside i marked with green arrows? - that the seal fits into Is it part of the case, or does it come out? It doesn't look great. As you can tell, this is my first time taking it apart. Thank you