Car rattles, worse with a/c on. Horrible trans fluid leak

For a couple weeks, my corolla has been rattling at idle. It is significantly worse when the a/c is running and it's too loud to find exactly where it is coming from, but it sounds like it's coming from inside the engine. I tried unplugging the spark plugs to see if it something with one of the cylinders, but when I unplug the individual plugs the noise gets worse. I ran the car for a couple seconds with the belt off and the noise did not go away. Its not the exhaust heat shield. I started it for just a couple minutes today to try once again to pinpoint the noise until I glanced under the car and noticed there was transmission fluid pouring out. This vehicle was just purchased used from a dealership and the warranty expired the day before the noise started and I was basically told to shove it. Any ideas would be greatly appreciated.