The driveshaft and transmission oil have NOTHING to do with each other. You will not lose a drop of tranny fluid with the driveshaft out, whether you drive it or not. However, you can lose transfer case oil with the driveshaft out, but never transmission fluid.
If you get tranny fluid out the back of your t-case....then you have serious problems!

Just for a try, rotate your driveshaft 180* and put it back on. There is a very slight possibility that the driveshaft is just out of balance, and rotating it might help some. Like I said, it a long shot, but heck, it only takes 5 minutes to find out.