You have 1 of 2 things happening.
1. The trans output/adapter input seal is leaking
OR
2. The t-case input is leaking due to a plugged vent.
In #2, the tcase doesn't create any pressure in the lube system. However, if the vent is plugged, then as operating temp rises in the case, then it will push fluid out the front & sometimes rear output seals. If it is #1, the trans will continue to push pressurized lube circuit fluid out and actually start to fill the t-case. Generally, if you pull yer t-case fill plug(the top plug). If its overfull, it's #1.
If it's low, then its #2. Just my 2 cents worth. Lou~