2015 GMC Sierra Denali HD Review

Stephen Elmer May. 06, 2014 Photos by Stephen Elmer

Self-proclaimed “truck guys” have a soft spot for big diesel engines that lay down massive amounts of torque and produce an elephant-sized rumble. Yet there is something about the GMC Sierra Denali HD that may turn this crowd off. It's quiet...too quiet.

FAST FACTS

Engine: 6.6-liter diesel with 765 lb-ft of torque and 397 hp.Transmission: Allison 6-speed Automatic. Tow Ratings: 22,900 lbs. with fifth wheel, 19,600 lbs. on ball hitch. Pricing: Sierra 3500 Denali starts at $51,735. 2500 Denali Starts at $51,635. As tested $67,500.

The rumble of the 6.6-liter diesel V8 is muffled behind a soundproof wall, a feature that will satisfy most buyers, but some people will miss the burly engine note.
This complaint, if you can call it that, is one of the defining characteristics in GM's latest round of trucks from the lowly V6 half-ton all the way up to the 3500 dually. They are noticeably more quiet thanks to aerodynamic enhancements including new inlaid doors that integrate much better into the body of the truck, reducing wind resistance and cabin noise.

Revamped Cabin

 

Highway cruising is very comfortable, partly because of how quiet the cabin is, but also because of the fully revamped interior for 2015. The insides introduced on the half-ton trucks migrate to the heavy-duty models for 2015 and that is a very good thing.

No other GM truck will provide quite the same level of luxury as the GMC Sierra Denali. It is set apart by its real aluminum trim accents, Denali badging and contrast stitching in the leather seats, but mostly an eight-inch fully digital display that sits right between the tachometer and speedometer.
The info cluster display is clear and easy to navigate and provides the driver with information on audio, navigation, fuel economy, oil pressure and battery life among other specs. The display is also configurable with three different layouts, which allows drivers a degree of customization that was previously unavailable.

Controls for the info cluster are mounted on the front face of the steering wheel and are rubber coated for a nice, tactile feel. Volume and radio controls are mounted on the back side: a strategy that permeates all Chrysler vehicles to reduce button clutter without sacrificing ergonomics.

Bright Chrome

But it isn't just the interior that sets apart the Denali. On the outside, all Denali-trimmed trucks are fitted with a massive chrome grille. Love it or hate it, you will stand out in this truck.
All GMCs are also fitted with unique projector-beam headlights with LED accents and plastic trim around the wheel arches, again to stand out better beside its Chevrolet sibling. GMC says roughly 33 percent of its customers choose the Denali trim, which almost makes it a sub-brand for the company.

There are also beefy-looking new Duramax badges on the hood that stand about a quarter-inch off the sheet metal. It makes the truck look tougher, but at the right angle, they can also send the sun flashing in your eyes. It won’t happen often, but it’s something that could be very annoying while trying to tow a trailer down a tight road.

No Crap, Just Heavy Duty

Now, on to the important stuff. Under the hood lives a 6.6-liter Duramx diesel that pumps out 765 lb-ft of torque and 397 hp mated to a six-speed transmission. As a pair, they are sold as a $8,395 option. For the more budget conscious customer, GM still offers a 6.0-liter gasoline powered engine that produces 360 hp and 380 lb-ft of torque. A compressed natural gas (CNG) option is also available on the 6.0-liter engine for a cost of $9,500. It allows the truck to run on both CNG and gasoline, controlled by the flip of a switch.

The real key to this pulling power lies with the Allison 1000 six-speed automatic transmission. Though both Ford's and Ram's heavy duty trucks put down more torque on paper, the GMC will actually pull away from both of those trucks while towing uphill in the real world. Needless to say, GMC arranged a head-to-head demonstration of that using 2500 series trucks from Ram and Ford. The GM products really did exhibit the smoothest shifts under a heavy load, and the power from the GMC simply felt more commanding than either of the others.

Towing Made Easy

GMC also introduced several new towing technologies that go a long way in improving how well the Sierra HD handles a trailer. A new exhaust brake uses the variable vane turbocharger for back pressure to help the engine control weight while rolling downhill, which has been combined with new auto-grade braking that works when the cruise control is engaged.
Simply put, if you set the cruise control to 60 MPH, the truck will do everything in its power to stay at 60 despite inclines or declines. It works.
We put this new technology to the test in a 3500 diesel dually. The downshifting transmission combined with the exhaust brake held back the weight of a 14,000-pound gooseneck trailer with relative ease without driver intervention. Even without cruise control turned on, the truck will automatically downshift to try and help to slow you down as soon as the brake pedal is touched. Rolling through the hills with a large amount of weight behind you has never been easier.
Out back, GM's new bumper-integrated step has been added and it works brilliantly, especially on HD trucks. With their higher ride height, the bed is even harder to climb into, and the step offers easy ingress and egress with no assembly required. Other small enhancements include LED lighting in the bed and eight tie-down locations, the upper of which are adjustable. These are a few small, smart add-ons that go a long way when you use your truck bed every single day.

The Verdict

By re-skinning its trucks for 2015, GMC now has smoothest riding, most comfortable heavy duty pickup money can buy. Sure to attract race horse owners everywhere, this truck is the Cadillac of the pickup world and makes a statement everywhere it goes.