Because the Germans do not need it ? That business about the extra 3rd gear sounds like doubletalk to me. Thought the Hemi got a six speed lockup trans with two overdrive ratios. Makes sense you might disable the MDS but I would tend to enagage the lockup more when towing to keep the trans temp down.
6th is a .67:1 vs a .83:1 for the V6. With a 3.09 gear the overal ratio in top/locked is 2.56:1 pushing a 30" tire. The V-8 has a 3.45 gear for a 2.31 top so for the same tire diameter, the V8 is turning 10% slower to help cruise MPG. Frankly the Hemi needs all the help it can get to help MPG. Both would probably be even better with a CVT but none (yet) can take the torque of either.
Interesting set of specs at http://www.automobile-catalog.com
, show the V8 being slower through the 1/4 than the V6 mainly because of a 600 lb higher curb weight.
Which brings up an interesting point to ponder: the EPA shows the same MPG range 17/23 2wd 16/23 4wd V6 87 PON, 14/20 2wd, 13/20 4wd V8 91 PON regardless of options. Personally suspect a 5000 lb Limited V6 with al the chrome options will not get as good MPG as a 4400 lb Laredo and the same for a V8. If I were to run a fuel economy rally, I'd even leave the full sized spare at home.