Pinion Seal Wont stop leaking

I have a 2004 KW W900 With RT40-145 Rockwell rears. Here's what is going on. I can not keep pinion seals in the front diff. I have chg the yoke, the vents and have went as far as putting a drop in diff in because I thought something was messed up in the diff. but here we are again with the same problem. The seals will last anywhere from 40-80,000 miles. It just like it isn't breathing enough and pressuring up the case. The seal will start as a slow leak and then start making a big mess. I have also taken out the through shaft and put new bearings in it when I put the drop in in. Also checked end play at this time. All was good. Also was told to check ride height and again it was right on. Could it be a out of balance drive line? If so wouldn't u feel a vibration? I am at a loss and don't know what to check next.
P.S. Maybe I'm just a lone sole and am the only one to have this problem. Ha Ha Thanks For any input.

 

Got a dumb ? Where or how do u go about doing that?

 

Don't think this is an issue. The diff is new/reman. I have had this problem since I bought the truck. Just can't get this figured out.

 

Had a buddy tell me the same thing kind of. He told me to go to a speedy sleeve seal. The seal that is in it is a stemco the one that is self turning. I am game for anything. It doesn't leak that bad right now but I just can't stand seeing that darn oil running down the diff.