The 6.7-liter Cummins diesel, Dodge's trump card in the one-ton marketplace, is a medium-duty straight-six, transplanted into a light truck. The Cummins is standard on the 3500. Even with intercooled, turbocharged induction, it is not a revver, making max horsepower at 3000 rpm. And it's not one of those engines that reacts instantly to throttle input. But what it does not offer in flexibility, it makes up in torque, durability, and fuel economy. It has a life-to-overhaul interval of 350,000 miles, 100,000 miles more than the competition. Oil-change intervals are 7500 miles, it holds 12 quarts of oil, and runs 29 quarts of coolant. If you have never seen a Cummins 6.7 crankshaft, it's worth a visit to the factory to check it out. Just don't try to pick it up.
the Ram's 6.7-liter I-6 turbodiesel...
the Ram's 6.7-liter I-6 turbodiesel doesn't require urea injection and comes with a six-speed manual or auto.
In theory, because it is a six, the 6.7 should get better mileage than the V-8 diesels in Ford and Chevy heavy-duty pickups, but that's hard to confirm because the EPA does not rate trucks over 8500 GVWR. In previous tests with the 6.7 Cummins, we averaged between 18 and 20 mpg on the highway. And, unlike the yet-to-be-released 2010-compliant Ford and Chevy diesels, Cummins has been able to meet stringent 2010 diesel emissions requirements without the use of urea injection. The Cummins can be had with either a six-speed automatic or a six-speed, granny-low manual transmission.
We drove a 3500 4x4 with the 6.7, both on back roads and on the highway. Even with the Cummins, the interior was quiet enough to make us forgot we had a diesel under the hood until we looked at the tach. Mated to the six-speed automatic, we saw 1750 rpm at 70 mph. In the unit we were driving, with hard-as-a-rock E-rated tires filled to max pressure, suspension tuning felt just slightly firmer than that of a Ford Super Duty. The front suspension uses coil springs, which are highly tunable, matched to appropriate leaf spring packages in the back.
There were only a few hundred miles on the odometer, and the 68RFE six-speed automatic had adopted a hard-shift mode, moving from gear to gear with a firm thump. We were told that the transmission is adaptive, "learning" to shift according to driver preference. And with journalists taking turns testing flat-out acceleration, the transmission had taken the hint. Over time, with gentle driving, the shifting logic would likely become more comfort-oriented.