Additionally, although fundamentally less complicated, we were equally impressed with the driving dynamics of the rearend. A new leaf spring strategy seems to have resulted in a smarter, quicker responding spring and shock combination. All 2011 HDs have wider and asymmetrical leaf springs to more quickly and firmly control the typical hopping motions heavy rear axles turning big torque numbers can generate. "Asymmetrical" means that the exact center point of the leaf spring is not directly over the axle. The new GM setup puts more spring over the back of the truck where they'll have more opportunity for the multi-stage flex of the spring to damp and cushion even more up and down forces. The result, as near as we could tell, in both empty and loaded scenarios (we drove several pickups, RWD and SRW, with 2000 pounds in the bed), was just about the most confident rearend we've experienced.
Another standout feature is that the steering feel is vastly improved over the previous generation. GM is now using a bigger gear box with stronger connecting shafts and arms that firm up the steering feel. GM has tuned in a firmer feel at highway speeds, while slower parking-lot speeds will feel lighter. Finally, our primary test unit came equipped the Vortec 6.0-liter gas engine, which is relatively unchanged with the exception of a new cam profile to lower the peak torque a few hundred rpm. The engine is rated for 360 horsepower and 380 lb-ft of torque and didn't have any problems keeping up with traffic but the 6L90-E did do a bit of gear hunting up steeper grades with some rough shifting between Three and Four. Our less-than-scientific average fuel economy came in around 15.2 mpg on our highway stretch with two large males and an empty pickup bed.
We did get to tow various types of trailers (fifth-wheel, flatbed, travel trailer) and, as you might expect, the new HDs seems to thrive in this environment, especially when equipped with the 6.6L V-8 Duramax turbodiesel. While driving a GMC Sierra HD 3500 HD 4x4 Dually with a fifth-wheel horse trailer loaded with lead ingots weighing about 13,000 pounds, we found the new Duramax pulls hard. The new variable vein turbocharger seems plenty fast enough to deliver strong off-the-line power and pulled our trailer up a grade from a dead stop to 55 mph. On the downgrade, we engaged the exhaust brake button (which uses the icon of an ice cream cone lying on the ground. Huh?) and hugely appreciated how the tow-haul mode aggressively uses aggressive downshifting and bigger brakes (now with 14-inch discs) to slow our heavy beast. We like that the same turbo that spooled up so fast to get us up over the hilltop is the same turbo that changes the fin angles to create back-pressure in the engine to slow it down on the backside of the grade. The dually diesel combination was impressive given our GVW must have been well over 21,000 pounds.