After you get over the "cool" factor for this mod the reason GM kept the batteries up front will become clear in a couple years. "Cool" is not the proper way to describe this mod, uncomplicated, needed, etc. just not 'Cool'. My point here is to inform people of the trade off made to do this. Then you can decide for yourself if you really care about the downside or just shrug your shoulders when it happens. My point is simply to discuss the downside and in no way slam the mod in any way.
GM violated this batteries up front setup on the Duramax trucks perhaps because some got laid off or retired. Simply forgot the reason they kept both bats up front. The reason is batteries run cooler up front not in the furnace that gets hotter closer to the firewall esp. with the fan kicked in.
Batteries HATE heat! The passenger side battery in the Duramax, that is not in the very front, nearly always fails first. The hotter the climate the worse this effect is. Climate is hot enough you pay for batteries once and exchange them every 2-3 years under warranty. Towing with the 2008 Duramax cross country, not always in AZ heat, got me 88K and 1.5 years before the passenger side battery gave it up while the other one was still good. Heat from the fan cooked it not just AZ weather.
After all the windshield washer bottle located over the tire on the fender: I evaporate more fluid out of that than I actually use due to the heat! GM located this bottle further upfront on newer trucks.
Uncomplicated intake trading off some battery life. After what it took to put the HX40II in I would take the trade off and possibly relocate the batteries in the bed or elsewhere to run them cooler. (The wet battery in patch lasted me 2 years and the Optima 3 years in our heat. Of course failing in August's 110+ temps.)
The cooler your climate and the less you hear the fan run the less this trade off applies to you. I would recommend a turbo blanket in all cases to keep the radiated heat off the battery.
