Ram's powerful 2500 and 3500 Heavy-Duty (HD) trucks return for 2015 with even more to like. Across the HD range, there's a choice between gasoline engines in the standard 5.7L and 6.4L Hemi V8s; as well as three versions of the 6.7L Cummins inline 6-cylinder diesel that top the range. All engines include a 6-speed automatic transmission, although a 6-speed manual transmission is offered with the diesel engine. The 5.7L Hemi is rated at 383 horsepower and 400 foot-pounds of torque. The 6.4L Hemi V8 makes 410 horsepower and 429 pound-feet of torque. With the 6-speed manual, the Cummins is rated at 350 horsepower and 660 foot-pounds of torque at just 1,500 rpm. When mated to the 6-speed automatic transmission, output jumps to 370 hp and 800 foot-pounds of torque. In Ram 3500 trucks with the top-duty Aisin automatic, it makes 385 hp and a staggering 865 foot-pounds of torque. High-pressure common-rail fuel injection helps aid refinement and clean up emissions and the Cummins is B20 biodiesel-blend compatible. Diesel Rams employ a Ram Active Air intake system that draws more cool air from the front of the truck for more power in hot temperatures or at high altitude. Also thanks to a variable-geometry turbocharger, Ram HD trucks have good responsiveness and drivability no matter what the load. Ram HDs can be ordered with either rear-wheel drive or 4-wheel drive. In 4-wheel-drive models, a front-axle disconnect system can help improve fuel economy by up to 1 mpg. The Ram 3500 utilizes a Hotchkiss leaf-spring rear suspension, while 2500s have replaced leaf springs with a 5-link coil spring setup. Front suspension is now courtesy of a 3-link system. 2500s can be optioned with heavy-duty air suspension in place of the coil springs, which allow for driver-controlled load leveling with precise, individual adjustment. Leaf-sprung 3500 dual-rear-wheel trucks with maximum tow packages also feature the air suspension system. Ram 2500 trucks benefit from a larger rear axle, 11.5 inches for 2015, while the high-output Cummins includes an 11.8-inch axle. The result is best-in-class towing and payload ratings for the 3500 (up to 30,000 lb and 7,320 lb, respectively) and best-in-class towing for the 2500 -- up to 17,940 lb. For the first time, Ram offers an optional fifth-wheel tow package. Ram understands that its trucks must last a lifetime. As a start, the company offers a 5-year, 100,000-mile warranty on all of its powertrains. Each truck also has extended maintenance cycles for fuel filters and oil changes, including a 15,000-mile interval on the Cummins diesel. Inside, Ram HD trucks have been reconfigured to allow for increased creature comforts. Available amenities include soft-touch instrument panels and door trim, 2-tone upholstery and contrasting stitching. Wood and metal inlays accent the interior and a largest-in-class 8.4-inch full-color touchscreen display serves as central command for the Ram HD. Heated and ventilated seating and a heated steering wheel are also available. Buyers can choose between bucket seats or a 40/20/40 bench configuration. In either case there's a multi-media port in the center with USB, SD and auxiliary inputs. Seven trim levels are offered: Tradesman, SLT, Big Horn, Laramie, Outdoorsman, Laramie Longhorn and Laramie Limited. These can be configured with either 2- or 4-wheel drive, 2-door Regular-cab, 4-door Crew-cab or 4-door Mega cabs. Two bed lengths are offered, a 6'4" or 8'. Ram's patented Ram Box can be equipped in several trims, adding a secure storage system in the sides of the bed. Each Ram HD offers a different set of interior appointments and equipment that can be tailored to fit basic work needs or provide a relatively luxurious cabin. Two different Uconnect systems with the 8.4-inch touchscreen are offered both with Bluetooth hands-free connectivity. The top system also provides wireless Internet connectivity, as well as HD Radio and SiriusXM compatibility. Top Laramie models offer impressive luxury and convenience, including a power-sliding rear window, leather upholstery, a heated steering wheel, dual-zone temperature control, an overhead console, a universal garage-door opener, and special in-floor storage. Available features include an Alpine 10-speaker premium audio system, rain-sensing wipers and projector beam headlamps.