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Why an independent rear suspension for GM's new, full-sized SUVs wasn't easy

A Motor Trend report last month laid out how Cadillac's 4.2-lier twin-turbo Blackwing V8 could be an orphan due to cost concerns in the GM empire. Last-minute chassis changes to Cadillac's new sedans and XT6 crossover led to engine bays that couldn't fit the Blackwing. On the SUV side, according to the report, the new independent rear suspension for big people haulers cost so much to implement that GM ruled out reworking the Escalade to accept the Blackwing. At least one commenter rightly asked how could a suspension swallow that much money. A new piece in Motor Trend has the answer. The excellent Alissa Priddle spoke to Tim Herrick, GM's executive chief engineer for full-size trucks, about why the clean-sheet IRS cost "multimillions of dollars."  First, GM would need to build a new body shop at the Arlington, Texas plant that assembles the automaker's big SUVs to stamp the numerous wholly new parts and panels accommodating an IRS. Then GM would need to design and pay for a new assembly process. On top of those up-front costs, there was the incremental cost of the four-link IRS components being more expensive than those in the trucks' former leaf-sprung solid axles. Herrick endured so many rejections for so long that he remembers the date and time when he got approval for the new unit. He said it came down to a meeting where he told a higher-up, "I'll make you a deal: If we get to the reveal, or if we launch this and you think this was a dumb idea, I'll hand you my badge and let you walk me out." Head to Motor Trend to read the full story. Based on Herrick being on stage to help present the new SUVs to the press, and on our First Ride in the new Chevrolet Tahoe and Suburban at GM's Milford Proving Grounds, it appears this will have a happy ending for all involved. Furthermore, since Herrick worked on the T1 platform that supports the big SUVs as well as the light- and heavy-duty pickups, he understood the demands on the commercial side, too. That could be why when Roadshow asked Tim Asoklis, chief engineer of the Tahoe and Suburban, if the new IRS could endure life in the Chevrolet Silverado and GMC Sierra, Asoklis answered, "Oh, absolutely." Related Video:    

Submit your questions for Autoblog Podcast #323 LIVE!

We're set to record Autoblog Podcast #323 tonight, and you can drop us your questions and comments regarding the rest of the week's news via our Q&A module below. Subscribe to the Autoblog Podcast in iTunes if you haven't already done so, and if you want to take it all in live, tune in to our UStream (audio only) channel at 10:00 PM Eastern tonight.
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2016 Chevy Volt will not need premium gas

Buried in the new technical details of the 2016 Chevy Volt released yesterday was a throwaway line about a small but important change that's due to the new 1.5-liter, four-cylinder engine. The first-gen Volt has always required premium gas but the new powerplant will be happy burning plain old regular. The Volt's chief engineer, Andrew Farah, told AutoblogGreen that the change was due to today's Volt owners explaining they were not happy paying for top-shelf petroleum. "The ability to use regular unleaded was based directly on customer feedback," he said. "Since the range extender is an all-new engine, it was optimized to use regular unleaded at the outset. Using regular fuel will not have effect on vehicle acceleration or other performance factors." As Larry Nitz, GM's executive director of vehicle electrification, told AutoblogGreen yesterday, the new engine is more powerful and quieter than the outgoing 1.4-liter engine that's used in the current Volt. Fuel economy and EV range specs for the next-gen Volt are not expected until the full car is revealed at the Detroit Auto Show in January.