This is a mod I did a probably a year and a half ago that I learned on a Dodge truck forum. It will increase your HEMI's transmission cooling capacity and is great for guys like us that pull decent sized trailers around. Dodge for a short period of time offered the HEMI motor in their 1 ton 3500 series pickups. I have seen only one in my lifetime. Most who need a 1 ton opted for the torque filled Cummins Turbo Diesel. But luckliy for us the HEMI was an option and Dodge included a extra large transmission cooler that is a direct swap for the smaller units that the 1500/2500 series gas trucks came with. This is about the simplest and easiest thing you could hope for all the mounting points and fittings/line connections will line up perfectly.
There were three different coolers offered and the replacement from the 1 ton is the largest. Below is a picture of the cooler my truck came with from the factory.
now here is the replacement ....
Just about tripled the size in my case. I know there is a cooler right in the middle of these two that came on some 1500's and 2500's but it is still smaller then this monster. If you look closley in the first pic you will see the empty mounting hole in the upper right corner that gets used with the swap. As I said everything is there just order it up and add some fluid due to the larger capacity. The Dodge part number is 52029089AB you can get it here Ram 3500 Parts
it is 170.50 much cheaper than a tranny rebuild and would take most guys about 30 mins to complete.