Is there a great transmission stop leak for my 2002 Mitsubishi Galant?

There are different products available. However, we are not allowed to recommend products. First, you need to determine if the leak is from a seal or a gasket. Once you do that, ask at a local parts store for a good stop leak that will help fix that type of problem. If the leak is at the trans pan, it's a gasket. If it appears to be coming from a different location, chances are it will be a seal.