GMC Sierra – First Drive: The whispers started probably two years ago. You remember: GMC is hurting...there’s no need for it...someone should introduce GMC to Olds... Ahhh. Nothing says professional grade like rumors about your demise. Then again, nothing says “I told you so” like a good run of new vehicles, which is exactly what happened. The new Sierra full-size pickup aims to continue the run, and it offers a big advantage over its mechanical twin, the Chevrolet Silverado: A model with a six-speed automatic transmission and a whopping 400 horsepower. Ouch. Now that’s a professional grade smack upside the chops if we’ve ever felt one.