The 2025 GMC Sierra 3500HD SLT is a heavy-duty pickup designed for strong towing capability and long-term durability with a more refined interior than base work trucks. It is powered by the 6.6L Duramax turbo-diesel V8 paired with the Allison 10-speed transmission, delivering exceptional torque and stability under heavy loads. The SLT trim adds upgraded comfort features, advanced towing technology, and premium styling, making it a balance between work capability and everyday usability.