Helping to smooth out the power delivery and engine braking is the latest Allison 1000 six-speed automatic transmission. Allison has gone through the box and wrung out every last bit of mechanical efficiency, all while beefing it up to handle the extra torque of the upgraded diesel motor. GMC boasts that the transmission has been specifically built to match either the gasoline or diesel engine for maximum efficiency and ideal gearing. Those sticking with gasoline will get an upgraded 6L90 six-speed automatic transmission, an upgrade from the 6L80 found on current models. The transmission controller, meanwhile, has been reprogrammed to work with a new exhaust brake on diesel models to keep braking as smooth and controlled as possible.
That's right, exhaust brake. Like the system that debuted on the Ram Heavy Duty, when activated the system increases exhaust backpressure and uses the diesel's high compression to slow the truck down. It isn't simply an on-off feature, either -- the system varies the engine braking depending on conditions to help slow the vehicle smoothly. When used with the cruise control, it can maintain the truck's speed down a grade without the driver having to step on the brakes, deactivating the cruise control.
Other features include a class-leading 250 lb-ft of torque available to the PTO, a Tow/Haul mode for better control and transmission safety, a cab warm-up feature that can increase the load on the engine on cold mornings to get the heater warmed up faster and manual shifting control. Gross Vehicle Weight Rating increases to 13,000 pounds and the Gross Combined Weight Rating jumps to 27,500 pounds while the Front Axle Weight Rating climbs to 6,000 pounds thanks to a heavily-revised independent front suspension. The truck's steering has been enhanced (a new, larger steering gear, power steering pumps and linkages) in order to better handle the increased front axle weight rating and reduce overall steering effort.
GMC says this upgraded front suspension is smoother riding and more easily adaptable to handle specific workloads than the competition. Backing it up is a new asymmetrical leaf-spring rear suspension with wider leafs, resulting in a higher payload capacity and less axle-hop. New shocks and hydraulic body mounts smooth everything out. What's more, any 4WD model can now be fitted with a snow plow. Slowing it all down are 14-inch brakes standard on all four corners to match the truck's increased weight and tow ratings.
All these impressive increases in capability come thanks to 11 all-new, fully-boxed frames to underpin the 11 cab and box configurations. GMC says the new frames are five times stiffer on their own while the hydroformed front sections are 125% stiffer. GMC even did the aftermarket a favor and added access holes in the frame for a gooseneck trailer hitch.
In the end, we're left with some important questions. Will GMC and Chevy best Ford in the power wars? Will the Sierra Denali HD be more comfortable and luxurious than the Ford Super Duty King Ranch? Does the Ram Heavy Duty stand a chance? We'll just have to get all the trucks together and find out. Stay tuned.