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GM opens official investigation into C8 Corvette transmission leaks

In March 2020, a month after Chevrolet began customer deliveries of the 2020 C8 Corvette, a GM dealer technician created a Reddit thread about a leaking gearbox in a Corvette with 32 miles. That car hadn't even been sold yet. Since then, as a search of "C8 Corvette transmission leak" shows, it's been tales of woe for some owners. Something in the Tremec TR-9080 transaxle in the back of the mid-engined Corvette doesn't work as it should, the fault able to cause codes that the transmission needs service, or that the driver needs to shift to park. In some cases, the battery would die because of follow-on issues after the initial transmission code, that code preventing the car from powering down. As Autoevolution reports, GM filed paperwork with the National Highway Traffic Safety Administration in August to look into what's going on. Between forum threads and GM's investigation document, there are several issues mentioned. The most common appears to be the dual-clutch transmission leaking fluid due to gasket failures like the one suffered by one owner at 858 miles, and another for an owner currently enduring a second leaking transmission. The Midengined Corvette Forum reported that Chevy engineers redesigned the TR-9080 pan, fitting Corvettes with the new unit at some point in the 2021 model year. The original pan was stamped steel unit affixed to the engine with two studs and 13 bolts, plus "reinforcement plates." The updated pan is said to be a cast aluminum unit affixed with two studs and 17 bolts, omits the reinforcement plates, and gets a new machined new groove around its edge to seat the gasket seal. The GM paperwork now at the NHTSA mentions a P1789 code, and says one reason for it could be "debris on the park position sensor magnet causing an incorrect position reading to the TCM." This might be caused by another issue mentioned in forums, which is clogged transmission filters. GM gives instructions for returning transmission filters to the company, and a poster on one forum said the Corvette tech at the dealer where he bought his Corvette told him the automaker "requires every used transmission filter to be returned to GM."  Whatever's going on, the problems haven't stopped, and they go beyond the P1789 code. Over the weekend, a 2022 Corvette owner posted on Corvette Forums that he got a check engine light on his car after just 850 miles.

GM exploring ways to raise half-ton Duramax diesel tow rating

Lots of truck owners cheered when GM announced fuel economy numbers for the 2020 Chevrolet Silverado with the 3.0-liter Duramax diesel inline-six. Even after Ram let loose its EPA mileage ratings for the 2020 Ram 1500 EcoDiesel, the Chevy oil-burner still took the trophy. The victory was years in the making, GM engineers spending an entire four-year development cycle refining the LM2 Duramax to increase mileage. The tradeoff, as well all know by now, is towing; the Duramax in half-ton duty pulls a maximum 9,300 pounds in the Silverado. Rivals across town can do more, the Ford F-150 PowerStroke rated at 11,500, the Ram 1500 EcoDiesel game to pull 12,560. GM engineer John Barta told Muscle Cars & Trucks that more hauling chops could be on the way, explaining, "We’re actually looking at upgrading some of the materials around (the engine bay) to see if we can maybe raise our tow rating." Engine bay materials are at issue due to thermal complexities underhood. John Barta, GM's assistant chief engineer of diesel engine controls, said the Duramax's inline-six configuration allowed engineers to get emissions hardware like the combined selective catalytic reduction, diesel oxidation catalysts, and diesel particulate filter unit closer to the engine, where it heats up quicker, getting emissions down quicker. But that filter puts another heat source in those confines, enforcing a cap on the tow rating to keep the engine and other systems from overheating. "If you look under the hood," he said, "youÂ’ll see a significant amount of silver ‘moon tapeÂ’ around to make sure things arenÂ’t getting overheatedÂ… if we were to go up in higher towing, which we can, we start impacting the possibility of deteriorating some of the components.” There isn't much space for more grille, so swapping for a better grade of "moon tape" or a different kind of material could reduce engine bay heat, extracting a higher tow rating in the process.  It's important to note a point Barta's been making for months about the Duramax figures, though. "Even though itÂ’s nice to brag about big numbers, in reality, light duty customers are not towing that large with their trucks," and, "We do know that (95 percent) of our light duty customers donÂ’t tow over 9,000 pounds." On our First Drive of the 2020 Silverado diesel we called out the tow rating, but emphasized that the Chevy and GMC have more important challenges to overcome.

2019 GMC Sierra AT4 gives Raptor and Ram a new off-road rival

The 2019 GMC Sierra AT4 blends off-road hardware into a modern, thoroughly updated pickup truck that doesn't skimp on power, luxury, or safety equipment. From its higher suspension setup to its available carbon-fiber cargo bed and the new MultiPro tailgate, the 2019 Sierra AT4 is a direct shot across the bow — or cargo beds, if you prefer — of staunch rivals like the Ford F-150, Dodge Ram and Toyota Tundra. Revealed tonight in New York City, ahead of this week's New York International Auto Show, the truck may seem to be in a strange setting. Then again, with the amount of tire-swallowing potholes currently scattered around the Big Apple, a rugged truck like the Sierra AT4 could be the perfect vehicle for either off-road excursions or an especially bumpy commute. Riding two inches higher than the standard 2019 Sierra, the AT4 comes with standard features like all-wheel-drive with a two-speed transfer case, locking rear differential, Rancho monotube shock absorbers designed specifically for off-roading, along with skid plates and 18- or 20-inch alloy wheels fitted with all-terrain tires or optional, mud-loving Goodyear Wrangler Duratecs. Hill descent control and GMC's Traction Select system are also standard. The latter of these two lets the driver choose between preset drive modes, suitable for various types of terrain and weather conditions. The system then adjusts throttle response, shift points, and the electronic stability control according to each mode. Related: 2018 GMC Sierra 1500 buying guide "The 2019 Sierra AT4 is designed for the customer who wants an elevated presence on the road and the capability to venture off life's beaten path," said Duncan Aldred, vice president of Global GMC. "It's also the beginning for the AT4 brand, which will be seen on every vehicle in our lineup in the next two years." Based on the new 2019 Chevrolet Silverado, the GMC Sierra (including the AT4 model) looks to stand out from its corporate cousin in terms luxury touches, along with some subtle exterior details. For the AT4, these visible differences include a body color grill surround and bumpers. Meanwhile, the inner grille, front fog-lights and faux fender vents feature a black-chrome finish. It's not flashy, which is probably exactly what GMC wanted for its upscale truck. The standard engine is a 5.3-liter V8, though buyers can choose an optional 3.0-liter turbo-diesel inline-six or 6.2-liter V8.