I believe Casey talked to you a few times, if it is leaking from the stub bearings then we have newer style stub retainers that seal better then the older style.
If it's leaking from the vent then you may need to add vent line to give it some breathing room. We loop the hose 3-4 times and zip tie it up above the cradle, this gives the diff room to breath before pushing diff fluid out.
This particular 9" kit was one of the older ones we made back when we first started making them.
Give us a call if you need anything else.