about one month ago I asked about how to replace rear differential pinion seal at 04 CTS. Now finally I fixed it. I appreciate for the advices from you guys. However, you dont have to make anything on pinion flange or nut, as the part you will get is a kit including flange, nut, and seal. The most important thing to install the pinion seal is to tight the pinion nut to 181 ft-lb.

The new parts are also different from the old ones. You have to figure out what part number you need. There are different designs on rear differential. You have to go underneath the car to find a casting number on the housing which will determine your part number.

if anyone needs some help on how to replace it, just shoot a email to applejuice.roma at gmail dot com.