Diesel vs gas......................

Unless you are in extreme conditions, you simply don't need one. And your transmission pan is not they key to success with your Allison - it is an awesome trans to begin with. I had one on my 99 F370 7.3 and when I had my transmission rebuilt (3x), my trans guy said that it was simply more oil to try to cool and the fins don't work that well because of the heat from under the truck. A larger pan won't reduce the temp, a better cooler will. You can also read more here.

Larger Tranny Pans...