For truckers needing to tow up to 31,200 pounds of trailer weight, or haul up to 7,390 pounds of cargo, the Ram HD series can deliver. The base engine is a 383-horsepower 5.7-liter V-8 (a.k.a. Hemi), while the 6.4-liter version steps up with 410 ponies. But the top HD performer is the six-cylinder Cummins turbo-diesel, available in three grades. The tamest is rated at 350 horsepower and 660 pound-feet of torque, while the intermediate delivers 370/800. For maximum grunt, the 385-horse version lays down 900 pound-feet. The Cummins is matched to a six-speed manual transmission (the only shift-it-yourself in its class), or a six-speed automatic. The V-8 engines perform with the six-speed auto box only. For maximum towing, a coil-sprung rear suspension with air bladders is available for 2500 models, while the 3500 uses optional air springs integrated into the existing leaf-spring suspension. The available four-wheel-drive’s disconnect feature disengages the forward driveshaft from the transfer case when not needed, thus slightly increasing fuel economy while reducing drivetrain wear and tear. The top-line Ram Tungsten Limited combines superior towing/hauling capacity with the latest in luxury and technology content.