I have a 1996 Astro w/ 4.3 and auto. 170,000 miles. I live in the northeast and at the end of last summer (2007) the transmission started leaking BAD only after driving 40 + miles on a 75 degree or hotter day, and only while on the throttle faily hard. As soon as I stop, leaving engine running, nothing drips. I can tell when its leaking by the clouds of smoke behind the van as it must be leaking diretcly on exhaust. A LOT of smoke. When you first start the van in the morning, I can accerate very hard for at least 30 miles w/ no smoke. And all winter long. (approx. 10,000 miles) w/ no transmission fluid added. I could drive as long as I wanted in the winter with no leak. Today was my first "long" drive on a "warm" day this year and sure enough, LOTS of smoke and the back of the van coated w/ oil film. (And tranny fluid low). Any ideas??