If the axle tube seal(s) are leaking, you will either see an oil residue or oil on the carrier plate (inside and/or outside), sometimes on the brake shoes themselves if leaking badly. You would also check the pinion seal as to sweating or leakage.
Make sure the housing vent is not clogged as this will also cause leakages.
There are special service tools to remove and install the end seals but you can cheat.
2240 is the retainer but also acts as an oil slinger/shield if the seal leaks.