E5USMC,
In my CSX (with same KMP diff as yours except you have the new billet cover
) I had a similar issue. During the install shakedowns, everything was great. Then on my first "long" drive (1 hr home) I found a big mess under the rear - gear
oil everywhere! I check the level and it was about .5" below the fill plug, so it was initially overfilled, got to a real operating temp and puked, and found its new level. It initially had a breather tube pointed down at about the same height as the diff, which I believe may have acted as a siphon. I installed a catch can inside the trunk like on my KMP and it's been dry since.
That drip from the fill plug was definitely a sign of it being overfilled (or the plug not nearly tight enough) but should have held anyways like patrickt said.
With the new fill level and can, you'll be fine.