This morning after sitting in the driveway for about 15 hours I started it and about 1/2 quart of fluid came out of the dipstick tube then stopped, nothing has been added or anything been done to the transmission lately. Seems fine now other than being about a half quart low and a heck of a mess in the driveway. Any idea what would cause this and is it likely to happen again?

Boil overs normally account for such situations. Since Ford recommends dropping and cleaning the pan, replacing the filter, and refilling with Mercon V ATF every 30,000 miles, I would have that done if it's time. Instead of using regular Mercon V, I use either Mobil 1 Synthetic Mult-Vehicle ATF or Amsoil Synthetic Universal ATF in my 2000 Taurus transmission and power steering unit.

I also have a 2004 Taurus and this has happened to me twice since I had the transmission serviced at 60,000 miles. The guy that worked on it said "they all do that".

My 2000 Taurus, with an AX4N transmission, has never done that, even in Texas summers running consistently above 100 degrees F. As you know, I only use full-synthetic ATF, which allows transmissions to run 25 to 50 degrees cooler than conventional ATF.

My 2000 sable spits oil out of the filler tube on a regulat basis.

I have a 2005 Ford Taurus and I just had my car in the shop and it was the little rubber vent cap was bad. So to save you money and time replace the cap first.

This is exactly what I was thinking. Any driveline component on any car has to vent somewhere. And the fill tube is not where it's supposed to.

At normal operating temperature, your transmission will build-up pressure. The vent is supposed to release the pressure, so that the seals remain intact and don't start to leak. In extreme heat, it is not uncommon for transmission fluid to "boil over," either through the vent and/or fill tube. This usually happens when you are stuck in traffic, with the air conditioner on and the transmission in drive. It's best, in these cases, to shift into neutral. This problem is also much more common on poorly maintained vehicles, where the cooling system is marginal. This causes the temperature in the ATX cooler to go higher yet. To help prevent boil overs, take good care of your vehicle's cooling system, ensure the vent cap is working properly, use full synthetic ATF, and install a supplemental transmission cooler. On trucks, it's a good ida install a transmission temperature gauge.