GMC Sierra Classic 3500 is a pickup truck manufactured by the General Motors Company (GMC). It is a heavy-duty pickup truck, available in both 2-wheel drive and 4-wheel drive models. It is distinguished from the GMC Sierra 1500 by its larger engine and payload. Commonly used for towing and hauling heavy loads, the Sierra 3500 has a 6.6-liter V8 engine, making it a diesel powerhouse.