OC tests the new GMC Sierra AT4 (at the Calgary Stampede!)

The folks from GMC also allow us a sneak peek at the first 2020 GMC Sierra HD AT4 in Canada (above). With a 6.6L Duramax Turbo diesel motor paired with an Allison 10-speed transmission, this baby has some serious power—it can tow up to 35,500 lbs. And with 15 built-in camera views, trailering in tight corners has never been easier.