Same issue only straight from the factory. My front seals started leaking prematurely. When I opened up to change them I couldn't find anything wrong with them. I did find however that the factory WAAAAY overfilled the axle.I have diff covers from solid. I let a shop replace my front inner seals and after the job was done my axle was leaking from both sides ALOT. 4 months later I drained the front diff and there was almost 3 quarts in it (after leaking for 4 months). When I contacted Solid they stated to fill using oem capacity's.
The long and short... I think the object here is to fill just to the bottom of the axle tube so your seals aren't BATHING in oil. The splashing of the oil will send enough lube down the tube so that they get lubricated instead of being literally submerged.