Chuck Lemont, a vehicle development engineer who works at GM's Milford Proving Grounds on vehicle acoustics, gave us insight on how the team made the cabin so quiet. He said the body had to be redesigned to incorporate the switch from rolled doors to inlaid doors. But there was a huge payoff: It allowed for the triple seals, which is something you see more in luxury cars, and made a big difference in reducing cabin noise. The dash mat on the engine side of the front dash now has greater coverage; there's better coverage in the acoustic back panel on the back of the truck; and the new headliner was designed to absorb more noise. They had to deal with the idea of "draining the swamp," where once you dramatically reduce cabin noise, you start to hear things you didn't hear before. As an example, the rest of the sound reduction was so good, engineers heard noises from the HVAC module they hadn't heard before. Something that previously would have been a slight squeak or rattle was suddenly noticeable, and had to be taken care of.
Braking upgrades focused on performance and reliability. While the front discs are a hair larger than before, the rear brakes have gone from 11.6-inch drums to 13.6-inch discs. When we took the Sierra to the track for performance testing, we observed that the 2014 needed only 125 feet to stop from 60 mph -- the previous generation took 150 feet to stop from 60. The brakes were also designed to be quieter and work with less vibration. Also, these brakes use Duralife brake rotors, an innovation first used on the Cadillac DTS, with a surface strengthened by a system called ferritic nitrocarburizing, where nitrogen and carbon are diffused into to the rotor, hardening it. Another benefit of this process is corrosion resistance. GMC anticipates these rotors could last twice as long as conventional rotors.
The 2014 Sierra team is filled with experience and enthusiasm. Many of these engineers have been working for the company for several decades, almost all in truck development. These are also the people who had been into cars and trucks as kids. One engineer mentioned that he took his dad's lawnmower apart to see how it worked, then was mostly successful at putting it back together. The team behind the new truck understands the needs of truck people, thanks to a combination of customer input, research, and experience, and put all that into the new models.
MEET THE TEAM
GMC's engineers were happy to talk about the Sierra.
Assistant Chief Engineer, EcoTec3 family of engines
GM Trailering Engineer, Milford proving ground
Vehicle Chief Engineer, GM full-size trucks
Chief Engineer and Program Manager, small-block engine family
Executive Chief Engineer, global full- and midsize trucks and SUVs
Vehicle Systems Engineer, full-size trucks
Vehicle Systems Engineer, body and exterior
Vehicle Development Engineer (vehicle acoustics), Milford proving ground