KC , There is a seal behind the drive flange you can replace . Just remove the axle and a little rubber cap thats covering the Snap-ring .  Take the Snap-off and wiggle/pull the flange off. You will see the seal.  Something to look at ,when you pull off the CV joint and gear oil runs out of the CV joint , You might find out that the little rubber cap is missing or it has a hole. This will look like that the seal is bad by slinging gear oil all over the side of the tranny and the main seal is OK.  When in doubt , replace both. Keep tabs on the 90w oil level and the oil cover plate gasket. They were prone to some pretty bad leakage.