2021 GMC SIERRA 1500 CREW CAB 3.0 TURBO DIESEL 4X4

If you're searching for a capable, fuel-efficient full-size truck, this 2021 GMC Sierra 1500 AT4 for sale at Pristine Cars & Trucks in Marietta, GA is worth a serious look. Powered by a 3.0-liter turbo-diesel inline-six, equipped with serious off-road credentials, and dressed in one of GMC's most sought-after trim levels, this crew cab pickup delivers the kind of real-world versatility that Georgia truck buyers demand — from job sites to weekend trails to long highway hauls.

Stock #MG178882 | VIN: 3GTU9EET3MG178882

About This 2021 GMC Sierra 1500 AT4 Crew Cab 3.0 Turbo Diesl 4x4

At 139,321 miles, this Sierra 1500 AT4 has been well used — and that's not a bad thing when you understand what these trucks are built to do. The 3.0-liter Duramax diesel engine in the Sierra 1500 is engineered for durability and longevity, with many diesel half-ton owners routinely crossing 200,000 miles with proper maintenance. For buyers in the Marietta area looking for a high-trim diesel truck without the new-vehicle price tag, this rig represents genuine value. The AT4 trim sits near the top of the Sierra lineup, meaning you're getting premium features that would have stickered well north of $60,000 when new.

The crew cab configuration means four full-size doors and a rear seat that comfortably fits adults — a practical choice for families, contractors, or anyone who hauls more than cargo. The 5 3/4-foot bed hits a sweet spot between usable cargo space and maneuverability in tight parking lots and neighborhoods across Cobb County.

2021 GMC Sierra 1500 Performance and Engine

The heart of this truck is the 3.0-liter turbocharged Duramax diesel, paired with a smooth-shifting 10-speed automatic transmission with overdrive. This combination is genuinely special in the half-ton segment. The Duramax 3.0 produces around 277 horsepower and 460 lb-ft of torque, but more importantly, it delivers that torque low in the rev range — which translates to confident towing, effortless passing, and real-world fuel economy that gasoline trucks simply can't match on highway runs.

The 10-speed automatic is calibrated to keep the engine in its powerband without feeling busy or hunting for gears. Whether you're merging onto I-75 with a loaded trailer or cruising up into the North Georgia mountains on a weekend trip, this drivetrain earns its keep. Four-wheel drive means you're covered when Georgia roads get slick in winter or when you need to venture off the beaten path.

GMC Sierra 1500 AT4 Features and Interior

The AT4 is GMC's off-road performance trim, and it packs a feature list that reflects its premium positioning. Expect a MultiPro tailgate — one of the most genuinely useful tailgate innovations in the industry — along with an off-road suspension tune, skid plates, hill descent control, and aggressive all-terrain tires from the factory.

Inside, the AT4 brings a level of refinement that surprises people who still think of trucks as rough-around-the-edges workhorses. The cabin features leather-appointed seating, a heated front row, a large infotainment display with Apple CarPlay and Android Auto, a premium audio system, and available wireless charging. The Sierra's interior design has earned consistent praise for its clean layout and high-quality materials — this is a truck you won't mind commuting in every day through Marietta and across Cobb County.

AT4 Off-Road Hardware

Beyond the cosmetic touches, the AT4 includes factory hardware that genuinely expands where you can take this truck. The two-inch factory lift, Rancho shocks, and skid plate protection mean this isn't just a styling package — it's a truck built to handle trails, gravel roads, and muddy worksites with confidence.

GMC Sierra 1500 Reliability and Ownership

The 2021 Sierra 1500 with the 3.0-liter Duramax diesel has developed a strong reputation among truck enthusiasts and long-haul drivers alike. The engine itself is a segment standout — light-duty diesel engines in half-ton trucks have a track record of outlasting their gasoline counterparts by significant margins when maintained properly. Owners consistently report strong fuel economy figures, often achieving 25-30 MPG on the highway, which helps offset diesel fuel costs at the pump.

The 10-speed Hydra-Matic transmission has proven reliable across GM's full-size truck lineup, and the AT4's mechanical hardware is shared with some of GMC's most durable configurations. As with any high-mileage diesel truck, reviewing maintenance records — particularly oil change intervals and fuel filter service — is always a smart step. Ask the team at Pristine Cars & Trucks about what service history is available on this vehicle.

Why Buy From Pristine Cars & Trucks in Marietta, GA

Pristine Cars & Trucks is located in Marietta, in the heart of Cobb County — one of metro Atlanta's most active and established used vehicle markets. Buying from a local, independent dealer means a more personal experience than you'll find at large franchise stores. The team at Pristine Cars & Trucks works directly with buyers to match the right vehicle to the right budget, without the high-pressure tactics that frustrate shoppers at big-box lots.

When you're spending serious money on a truck like this Sierra AT4, knowing and trusting who you're buying from matters. Pristine Cars & Trucks has built its reputation in the Marietta community on straightforward deals and quality inventory — and a diesel-powered, high-trim Sierra 1500 speaks for itself as a vehicle they stand behind.

Financing a Used GMC Sierra Near Marietta

Financing a used truck at this price point is more accessible than many buyers expect — especially in Marietta and across Cobb County, where the team at Pristine Cars & Trucks works with a range of lending sources to help buyers find competitive rates. Whether you have excellent credit, are rebuilding your credit history, or are somewhere in between, it's worth having the conversation before assuming what's possible.

Putting together a realistic monthly payment on a truck like this Sierra AT4 often surprises buyers in a good way, particularly when the trade-in value of your current vehicle is factored in. Call Pristine Cars & Trucks at 770-941-1194 to discuss your financing options before you even come in — it saves time and sets clear expectations.

Frequently Asked Questions

Is the 2021 GMC Sierra 1500 AT4 a good buy?

Yes — the 2021 Sierra 1500 AT4 is considered one of the better full-size truck packages available from the 2019-2021 generation. The AT4 trim combines genuine off-road capability with a premium interior, and the Duramax diesel engine option makes it one of the most fuel-efficient and long-lasting choices in the half-ton segment.
 

How many miles is too many for a diesel Sierra 1500?

With proper maintenance, the 3.0-liter Duramax diesel can comfortably reach 200,000-250,000 miles. At 139,321 miles, this truck has plenty of useful life remaining — particularly for diesel buyers who understand how these engines are built for longevity. Review the service records and pay attention to oil change history and fuel filter maintenance intervals.
 

What does the Sierra 1500 AT4 trim include?

The AT4 trim includes off-road-specific hardware like a factory lift, Rancho shocks, skid plates, and all-terrain tires, along with premium interior features such as leather seating, heated front seats, a large infotainment touchscreen with Apple CarPlay and Android Auto, the MultiPro tailgate, and a premium audio system. It's positioned as GMC's adventure-ready, premium off-road package.
 

What is the fuel economy of the 2021 Sierra 1500 diesel?

The 3.0-liter Duramax diesel-powered Sierra 1500 is EPA-rated at approximately 23 MPG city and 30 MPG highway — exceptional numbers for a full-size crew cab 4WD pickup truck. Real-world highway mileage often meets or exceeds those figures for long-haul drivers.
 

Is the 3.0-liter Duramax diesel reliable?

Yes — the 3.0-liter Duramax in the Sierra 1500 has been well-received by owners and reviewers since its introduction. It's a purpose-built light-duty diesel with a strong reliability record and is widely considered one of the best half-ton diesel options currently on the market.

Serving Marietta and Surrounding Areas

Pristine Cars & Trucks is proud to serve buyers throughout Marietta and the greater Cobb County area, including customers traveling in from Kennesaw, Smyrna, Acworth, Powder Springs, Woodstock, and communities across Cherokee and Paulding counties. The dealership is also an easy drive for buyers coming from Roswell, Alpharetta, and other parts of metro Atlanta who want to see quality used truck inventory without fighting into the city.

If you're searching for a used GMC Sierra 1500 near Marietta or in Cobb County and want a diesel-powered, off-road-capable crew cab, this AT4 is one of the stronger options you'll find in the region. Don't wait — trucks like this at this price point move quickly in the Atlanta metro market.

Contact Pristine Cars & Trucks Today

Ready to see this 2021 GMC Sierra 1500 AT4 in person? Contact Pristine Cars & Trucks in Marietta, GA at 770-941-1194 to schedule a test drive, ask about the vehicle's service history, or get a head start on financing. The team is ready to help you drive home in the truck you actually want — not just what's available everywhere else.