The Sierra full-sized pickup is competent all around. The interior is quiet and roomy, handling and braking are good for a truck. The four-door extended-cab versions are also the only such pickups with habitable rear seats. The front seats are not particularly supportive. Four-wheel-drive models offer a selectable system with a full-time mode. The Sierra Denali is an expensive AWD model with a 6.0-liter V8 and four-wheel-steering called Quadrasteer (also available on the Heavy Duty models), which enhances maneuverability in tight spaces and improves stability while towing.