Transmission leaks when hot

bcole6

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??

dlm1954

Are you sure your not checking it cold and then over filling it, that what it sounds like overfilling may not be problem in inclement weather because the fluid would not get hot enoungh to expand but in hot weather tranny fluids expands to a point that it may be forcing it out because of the expansion.

bcole6

No, not over filled. When leaking for more than 5 minutes (smoking) tranny runs low and van stops. I always stop a little sooner and add fluid. Van always runs and shifts perfect after fluid is adde