For this final round, the stakes were raised: A 6.0-liter-powered GM with a towing package is the most direct comparison to the Tundra with the 5.7, and we added weight in two forms. Ding, ding! Cue the ring-card girls.
GM's latest 6.0-liter adds active fuel management and variable valve timing to its single-cam pushrod aluminum block. It's rated at 367 horsepower at 5500 rpm and 375 pound-feet at 4300 rpm, just 14 and 26, respectively, shy of the Tundra. The Toyota also has the wider powerband on paper with 2000 rpm between peaks as opposed to the 6.0-liter's 1200 rpm.
Margins like that seem almost insignificant and might be with equal gearing. However, gearing isn't equal, with Tundra's 4.30:1 axle ratio besting GM's shortest-available 4.10:1, and the disparity in gear choices. Combine the Toyota's higher output with deeper gears, and it puts nearly 20 percent more twist to the wheels in first gear and the gap widens from there (see sidebar, "The Gear Box"). With $23,000 cars and SUVs sporting six-speed automatics, the General can't get them in $35,000 pickups soon enough.
Those advantages translate to enough extra grunt that the Tundra accelerated an average of 18 percent quicker in our battery of towing tests, which included grades, 0-to-65, 45-to-65, and 20-to-65 mph, the last because even when towing a heavy load, the Tundra's engine spun the tires to invoke traction control at starts. And with more gear choices to optimize efficiency, the Tundra averaged 15 percent better fuel economy in the process. We watched the readouts carefully and didn't see the GMC's V-4 mode display very often, noting it primarily at drop throttle. In EPA rankings, the GMC rates 1.0 mpg better, numbers our real-world exercises (towing, hauling, highway, city) didn't agree with.
At the building supply center, we forked more than a ton of cement bags into the Tundra and drove the truck over to the GMC (which was parked away from the loading dock), where half the cement was offloaded into the Sierra's bed. Despite being roughly 850 pounds beyond weight limits, the Tundra still had some compression travel left in the rear leafs. Loads matched, we hit the road, experiencing surfaces that were good, marginal, and bad.
Everything we liked about the GM from Round 2 was here: Comfortable seats, simple, clean dash design, nicely weighted precise steering with good feedback, and a ride that was well controlled, partly because it was still about 600 pounds below GVWR. Whoop-de-doos didn't get it airborne. It has stiffer spring rates and a lower profile than the Tundra, which kept it flatter. Also, at least one pilot preferred the Z85/NHT "handling/MAX trailering" suspension to the Z60 setup used in the previous round. Testers noted the GMC felt more controlled when running quickly down the winding roads, which is attributed to the firmer suspension, lower ride height (and probably lower center of gravity), and the perceived security from higher window sills. It's worth mentioning that because of an aluminum block, disc brakes, and smaller wheels, this 6.0-liter VortecMAX truck weighs 159 pounds less than a cast-iron 5.3-liter/Z60 with drum brakes and 20-inch wheels.
Naturally, there were a few exceptions. The more truck and trail-appropriate Wranglers made the GMC cabin the noisier of the two, and the 6.0-liter's rear discs gave better feel and welcome added fade resistance charging down eight- to 12-percent hills. Last and least important, the interior lacks the same warmth and flair in black that it does in lighter hues. In general, the GMC's controls are more solid and more communicative than the Tundra's, becoming a distraction only during maneuvering as we outpaced the Sierra's steering pump twice.