2011 Chicago Auto Show: Ram Increasing Heavy Duty Diesel Power Ratings

Update 1: Feb-11-2011 10:31 am PT

We reported earlier that horsepower for the new High Output 6.7-liter I-6 Cummins would be able to climb to 390 hp under certain conditions. That was incorrect. Peak horsepower remains 350 hp, the same as the current Cummins 6.7.

"The peak horsepower doesn't go up," said Mike Cairns, Ram Heavy Duty chief engineer. "Horsepower at various RPMs is higher [than before]. It's about 23 percent higher at 1,600 rpm, which is where we now hit the peak torque rating. Horsepower is about 244 horse [at the rear wheels]. The peak is the same but at the working RPM level you're getting about a 23 percent boost."

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The battle between Ford and General Motors for towing and hauling bragging rights in the heavy-duty truck segment has been brutal — especially for Chrysler's Ram division. No longer. Ram Truck has announced midyear powertrain and towing upgrades to its 2011 2500 and 3500 Heavy Duty truck line up that will give it best-in-class trailer towing ratings amongst one-ton trucks.

"Get a load of this new bad boy," said Fred Diaz, Ram's CEO introducing a Ram 3500 with the new High Output Cummins 6.7-liter I-6 diesel. "It's guaranteed to defend the title as the most capable truck on the planet."

The High Output 6.7-L Cummins I-6 engine increases torque 23 percent to 800 pounds-feet (@ 1,600 rpm), up from today's rating of 650 pounds-feet (@ 1,500 rpm). It will be standard on all 2500 and 3500 models equipped with Chrysler's 68RFE six-speed automatic transmission. The transmission also gets a new torque converter with updated shift calibrations to handle the increased power. There's also a new crankshaft damper that's said to reduce engine noise and vibration.

Horsepower for the Cummins remains 350 hp (@3,000 rpm), the same as today.

Above are the new dyno charts for the High Output Cummins 6.7 vs. the current Cummins 6.7.

Ram HD pickups with six-speed manual transmissions will keep today's Cummins diesel and 350 hp, 650 lbs.-ft. torque ratings.

Ram HD towing ratings are also headed upward, with an optional Max Tow package that will increase fifth wheel towing to 22,700 pounds on select Ram 3500 one-ton models, up from today's 18,500 pounds rating. The max gross combined weight rating will also rise to as high as 30,000 pounds.

To handle the increased towing, the Max Tow package will add a beefed up rear axle with a new 4.10 gear ratio, new rear-axle pinion, new helical gears, upgraded bearings and an aluminum differential cover with large cooling fins. There's also a new water-to-oil transmission cooler and new power steering cooler to help manage the higher trailer towing ratings.

Diaz said Ram will continue to not require the use of desel exhaust fluid to meet emissions. It will remain urea-free, using Cummins technology to reduce NOx without DEF refills.

The High Output Cummins I-6 and Max Tow package for Ram 2500 and 3500 HD goes on sale in the second quarter of this year.