All good things come with compromise, and the Power Wagon is no exception. Thanks to its soft off-road-oriented suspension, it sports the lowest payload and tow capacity of the Ram 2500 lineup, at 1,660 pounds and 10,330 pounds, respectively. After breezing along with a 7,500-pound trailer—roughly three-quarters of its max tow capacity—we attached a 10,500-pound trailer. People go over weight all the time, so why not see what happens?
Answer? Not much. Thanks to the gobs of power produced by its 6.4-liter V-8 and its well-geared transmission, the legally overstressed Power Wagon proved that chasing max tow numbers is a fool's errand, as it handily out-dragged the Silverado 2500 with the same trailer. "That's max tow?" Evans asked. "No doubt at all it's suspension-limited. It feels like it could take thousands of pounds more and still accelerate better than GM's gas 2500s."
This is from motortrends article. This is why the 6.4l hasn't been improved upon. The 8spd did all it needed too.
So, if it ain't broke don't fix it is their marketing scheme