A couple of months ago, one of the transmission cooler lines blew off of my transmission as I was driving at full highway speed.
First indication I got was a huge cloud of smoke trailing behind me and blocking my vision of all of the other vehicles behind me on the interstate highway.
I quickly made a bee line for the right hand shoulder of the highway to assess the situation.
When I looked under the passenger side of the truck, the entire underside was covered in some kind of oil.
I had the truck towed to my mechanic's shop.
The next day, they had to have the truck dragged into the lift bay since it could not move under it's own power.
It was determined that the cooler line had disconnected somehow from it's port on the side of the transmission.
They reconnected the line and made sure it was seated firmly and properly.
I went ahead and had them drop the pan and replace the filter and top off the transmission fluid.
This amounted to nothing more than an unscheduled transmission fluid and filter service for my truck.
My last transmission rebuild was 6 years and 100K miles ago.
This event was several thousands of miles ago including a long vacation trip down to the Gulf Coast.
I am seeing no ill effects, so far.