As Kelley Blue Book points out, the GMC Sierra 1500 AT4 is the most capable full-size pickup that General Motors makes, alongside the Sierra AT4’s corporate cousin, the Chevy Silverado 1500 Trail Boss. To that end, the GMC Sierra AT4 includes a list of upgrades over the standard line of GMC Sierra 1500 pickups, including a factory suspension lift adding an additional two inches of ride height. The AT4 also runs a set of 32-inch Goodyear Duratrac tires, and upgraded Rancho shocks as well. In the nose, the AT4 deletes the front air dam to provide extra off-roading clearance on steep inclines.
Further upgrades for the GMC Sierra AT4 include a two-speed transfer case, a locking rear differential, hill descent control, a high-capacity intake, integrated dual exhaust, and a set of skid plates to protect the greasy bits underneath.
In addition to recognizing the 2021 GMC Sierra 1500 AT4, Kelley Blue Book also recognized the 2021 Chevy Colorado ZR2 in its list of the Best Off-Road Trucks currently on sale.
“It’s a solid package that fits nicely in between a more extreme Raptor or TRX and a standard-issue 4×4 pickup,” Kelley Blue Book writes with regard to the Sierra 1500 AT4. “The ride quality on road and off is smooth and the chassis has just enough off-road capability to have fun in the dirt.”
As for the engine spec, the GMC AT4 is equipped as standard with the 5.3L V8 L84 gasoline engine, while the naturally aspirated 6.2L V8 L87 and 3.0L I6 LM2 turbodiesel Duramax are both optional. Output is rated at 355 horsepower and 383 pound-feet of torque with the L84, 420 horsepower and 460 pound-feet of torque with the L87, and 277 horsepower and 460 pound-feet of torque with the LM2.
“Our test model was fitted with the excellent 420-horsepower 6.2L V8, the Sierra’s top-of-the-line engine,” writes Kelley Blue Book’s Matt Degen. “This big V8 has a healthy growl, and power off the line is smooth and quick. The 10-speed automatic offers quick response when you accelerate, and power delivery is easy and rewarding. Shifts are smooth, not jumpy, and can be quickened when you engage the Sport drive mode.”
Source: Kelley Blue Book