I didn't notice till today that there's some oil grease leak on the wheel, I'm not sure if the bearing seal is leaking. The leakage is showing on one of the front wheel and one of the rear wheel. I did the front wheel bearing repacking 3 years ago at 30k. Didn't do nothing on the rear wheel bearing though.

Can someone please give me some idea what it might be? Is the bearing seal broken and I need to repack the bearing? I remember for some reason the rear bearing needn't to be repacked, not sure why. BTW, on my 60k service, they drained and refilled the differential fluid. Could it be the cause for the leak on the rear wheel axle? But the symptom looks almost the same both front and rear wheel.