car in storage and something broke and leaked

What is your question?

My mustang was in storage for over a year when I noticed a very large puddle under the vehicle. It was not an oil substance and farther back than the radiator. I am thinking maybe transmission seal failure, it was toward the back of the engine under the vehicle. The puddle was more like radiator fluid than anything else? What seal would fail and is that an expensive repair?? The car has always ran fine.