Driving to the store one day, I noticed the transmission slipping and not up-shifting. Fortunately I was only 2 miles from home. When I got the car back to my house I inspected and noticed two problems. One, the coolant overflow tank was actually "overflowing", and two, the transmission dip-stick was bone dry. I added a quart of transmission fluid and limped to the Honda dealer(they are much closer than the Acura dealer). They investigated and told me the problem. There is a transmission line that runs through the radiator to help cool the transmission fluid. At the point where it enters the radiator, it cracked (inside the radiator). When the engine is running the trans fluid is under pressure and is forced into the cooling system. Some coolant can leak into the transmission but, fortunately, not much. Because there was not any significant damage to my transmission the fix was new radiator and hoses and flush both systems twice. It was a fairly expensive fix and I was without my vehicle for several days. But I was also fairly lucky. If this happened while driving high speed or some place away from civilization it could easily have fried my transmission.