The Fast Lane Truck (TFLT) works hard to compare all the best available trucks on the market. In their latest video, they put the GMC Sierra HD AT4X AEV with overland and camper goodies to the ultimate test on the Rocky Mountain Tombstone Hill trail in Colorado. Andre Smirnov, the Managing Editor of TFLT, took the Sierra off-roading to tell us the details.
The 2026 GMC Sierra HD
The 2026 GMC Sierra HD is available in either 2500 or 3500 and can be optioned with two popular engines, the 6.6-liter gas V8 with 401 horsepower and 464 lb-ft of torque or the Duramax 6.6-liter V8 turbo-diesel with 470 horsepower and a monstrous 975 lb-ft of torque. Both engines are mated to an Allison 10-speed automatic transmission that ensures to make life easier no matter what you’re doing, whether that’s towing up to 18,475 lbs in gas form or 20,000 in diesel guise, or going off-roading on extreme trails, like TFLT did in this video. The truck used in this video is powered by the Duramax diesel.
Pricing and Configurations
The Sierra 2500HD has a starting price of $47,000 while the 3500HD starts from $47,900. Both can be configured in either a regular cab with a long bed, double cab with a standard or long bed, or a crew cab with a standard or long bed. Both can also seat up to six passengers.
What’s Been Added to This Special Sierra HD
The particular Sierra HD used in the video costs $175,000 and features special American Expedition Vehicles (AEV) treatment that hasn’t been available on the Sierra until now. The truck has 37-inch tire clearance kit with 37x13.5-inch all-terrain tires that use a different offset for the Salta HD wheels to make sure the tires don’t rub when turning. The model features a front lightbar that AEV says is a prototype that still uses the stock camera and washer system. The tires, offset, and clearance kit are all very special and unique to this truck and will soon be offered to buyers. The stock Multimatic DSSV shocks remain since they are proven to work brilliantly. This is a truck made to have no compromises.
This Truck Is FAST
Amazingly, even though this special GMC Sierra weighs more than 10,000 lbs, Andre was able to get it from 0 to 60 mph in 9.2 seconds in 4WD mode and 9.1 seconds in 2WD, which is incredibly fast. He said, “... especially passing maneuvers, this truck screams.” Keep in mind, The Fast Lane Truck is based in Colorado, a mile above sea level.
Fuel Efficiency
While fuel mileage may not be the first thing you think of when building an overland vehicle, it can still be important. This specific Sierra HD build, again weighing about 10,000 lbs, was able to average 14 mpg over a 78.2-mile drive, using only 5.6 gallons of diesel fuel. That’s actually quite efficient when you factor in the not-so-aerodynamic camper on the back and the 37-inch-tall all-terrain tires.
Auctioned Off to Benefit Charity
Andre reports that the GMC Sierra HD AT4X AEV tested can be optioned to your specifications. The one used in this video was sold at auction with proceeds going to charity.
Dieffenbach GMC Is the Home of Your Next Car
When you feel the time is right to pick up your own GMC Sierra, whether it be a 1500 or HD model, the best place to go to compare all options and trim levels is Dieffenbach GMC. The well-versed sales staff will help you feel comfortable making the decision that’s best for your needs and budget.
Why Choose Dieffenbach GMC
Dieffenbach GMC takes great pride in offering outstanding sales and service for our customers. Whether you are looking for a new or used car, our sales team and finance department will ensure you get the best price. And our service department will take great care of your vehicle.