I have a 300D. I recently had a Transmission leak too! I had put this stuff called "No Leak" for transmissions in. You can pick it up at Wal=Mart for about $5.00! It takes a few hundred miles to work, but it really works! I also use the one designed for oil leaks in the engine. Just for fun, you might want to try this. Until you have the courage to spend the $$$ on a rebuild!