While I understand the position that NO leak is acceptable, if we think about this on a practical basis, fluid "weeps" are usually not a problem. Consider:
In the 68RFE, the fluid level must usually be about 4 quarts (or more) low before you experience obvious symptoms (slippage, strange operation, etc.). Four quarts = 3,785 ml = about 75,700 drops. So, let's suppose you had a leak that was losing 10 drops per day (much worse than a "weep," and one that would certainly leave spots on the driveway). At that rate, it would take well over 20 YEARS before you lost 4 quarts of fluid.
Now I'm not trying to say that a 10-drop-per-day leak is acceptable (it isn't!). Just want to give some perspective on why I think "wet dirt" really shouldn't be a concern.