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1620 East Homer Adams Pkwy Alton, IL 62002

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2025 GMC Sierra HD AT4 OVERVIEW Overview Icon

2025 GMC Sierra HD AT4 in Alton

  • 6.6L V8 Gas engine
  • Allison® 10-speed automatic transmission
  • Remote Keyless Entry
  • Automatic Emergency Braking
2025 GMC Sierra HD AT4 Main Img

2025 GMC Sierra HD AT4 MODELS

  • Sierra HD AT4

    Sierra HD AT4

  • Sierra HD AT4 AT4X

    Sierra HD AT4 AT4X

GMC Sierra HD AT4 Dealer in Alton

2025 GMC Sierra HD AT4 PERFORMANCE Performance Icon

2025 GMC Sierra HD AT4 performance

DURAMAX 6.6L TURBO-DIESEL V8 ENGINE

Sierra Heavy Duty’s available Duramax 6.6L Turbo-Diesel V8 engine features an efficient turbocharger and Allison 10-speed automatic transmission.

2025 GMC Sierra HD AT4 performance

AT4 OFF-ROAD READINESS

AT4 features an off-road suspension with twin-tube Rancho shocks, skid plates and Hill Descent Control, which uses antilock braking to help you maintain control.

2025 GMC Sierra HD AT4 performance

PROGRADE® TRAILERING TECH

This advanced suite of available intelligent technologies helps streamline the hitching and towing process with integrated tools that help enhance your sense of confidence and visibility.

2025 GMC Sierra HD AT4 APPEARANCE Appearance Icon

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2025 GMC Sierra HD AT4 appearance

AT4 GRILLE

Stand out with AT4’s bold front-facing exterior design and LED projector headlamps with animated sequences.

2025 GMC Sierra HD AT4 appearance

20" AT4 WHEELS

Sierra HD AT4’s 20" gloss-black aluminum wheels with available BFGoodrich off-road tires are made for rough trails.

2025 GMC Sierra HD AT4 appearance

SPRAY-ON BEDLINER

Help protect the bed and enhance its style with durable cargo bed protection featuring a GMC logo.

2025 GMC Sierra HD AT4 COMFORT Comfort Icon

2025 GMC Sierra HD AT4 comfort

AT4X EXCLUSIVE OBSIDIAN RUSH INTERIOR

AT4X’s interior features authentic Vanta Ash wood, and seats include bold red and white double-needle stitching for athletic character.

2025 GMC Sierra HD AT4 comfort

PREMIUM ALL-WEATHER FLOOR LINERS

Help protect your interior with available floor liners with removable carpet inserts.

2025 GMC Sierra HD AT4 comfort

PREMIUM GMC INFOTAINMENT SYSTEM*

With available Google built-in compatibility,* this system offers a helpful, personalized and seamless way to enhance the entertainment in your truck.

2025 GMC Sierra HD AT4 SAFETY & WARRANTY Safety Icon

PRO GRADE PROTECTION

Standard on every new GMC - GMC Pro Grade Protection has you truly protected with features and services including:

  • 3-year / 36,000-mile Bumper-to-Bumper Limited Warranty
  • 5-year / 60,000-mile Powertrain Limited Warranty
  • 5-year / 60,000-mile Roadside Assistance & Courtesy Transportation
  • 3-year / 36,000-mile Corrosion Protection
  • 6-year / 100,000-mile Rust-Through Protection
  • First maintenance visit
2025 GMC Sierra HD AT4 Safety Main Img
2025 GMC Sierra HD AT4 safety

REAR PARK ASSIST

Rear Park Assist* can provide distance alerts to nearby detected objects behind your vehicle to help you park and avoid collisions when you’re in Reverse at low speeds.

*Feature will not function on certain models without dealer retrofit; see dealer for details.

2025 GMC Sierra HD AT4 safety

BLIND ZONE STEERING ASSIST

Blind Zone Steering Assist can provide a brief, firm turn of the steering wheel when a potential collision is detected with a moving vehicle in the lane you’re entering.

2025 GMC Sierra HD AT4 safety

FORWARD COLLISION ALERT

Forward Collision Alert can warn you if it detects a potential front-end collision with a vehicle you’re following so you can quickly take action. It can also provide a tailgating alert if you’re following a vehicle much too closely.

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