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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 recalls 3.8 million vehicles in North America due to braking issue

WASHINGTON — General Motors Co said Wednesday it was recalling 3.46 million U.S. pickup trucks and SUVs to address a vacuum pump issue that could make braking more difficult and that has been linked to 113 accidents and 13 injuries. The recall covers 2014-2018 model year vehicles, including some Cadillac Escalade, Chevrolet Silverado, Chevrolet Tahoe, GMC Sierra, Chevrolet Suburban and GMC Yukon vehicles. In late June, GM recalled 310,000 vehicles in Canada for the same issue. GM did not immediately explain why the Canadian recall occurred more than two months before it called back the vehicles in the United States. The recall was triggered because the amount of vacuum created by the vacuum pump may decrease over time, GM told the National Highway Traffic Safety Administration (NHTSA) in documents posted on Wednesday. The NHTSA opened a preliminary investigation into the issue last November, and said it had reports of nine related crashes and two injuries. It provided GM in July with additional field reports that prompted the automaker to open an investigation. GM said it could affect braking in "rare circumstances." The NHTSA said in a statement the "vehicles may experience brake boost failure, which would require increased brake pedal effort, leading to a hard brake pedal feel, and potentially increased stopping distance." GM said dealers will reprogram the electronic brake control module to improve how the system utilizes the hydraulic brake boost assist function when vacuum assist is depleted. GM said the vacuum assist pump, which is lubricated with engine oil that flows into the pump through a filter screen, can in some cases lose effectiveness over time, as debris such as oil sludge can accumulate on the filter screen. GM told NHTSA that prior model years used a different brake assist system design, and vehicles manufactured after 2018 were not equipped with the affected pump design. Separately, GM said on Wednesday it is recalling 270,000 additional U.S. vehicles in three smaller recalls, including 177,000 2018 Chevrolet Malibu cars with 1.5L turbo engines because an error in the engine control module software may result in the fuel injectors being disabled.

2022 Chevy Tahoe, Suburban and GMC Yukon get updated transmission

General Motors' full-sized SUVs have slipped in one more change before the year turns. GM Authority reports that the 2022 Chevrolet Tahoe and Suburban, and the 2022 GMC Yukon and Yukon XL equipped with gas V8 engines, will pick up a revised ten-speed automatic transmission. The new unit carries RPO code MHS, and Chevrolet communications rep Catherine Scales told GMA the updated gearbox "allows our manufacturing and dealer teams to more easily align the specific calibration needed for the transmission and can enable OTA updates in the future." It seems GM wants to make it easier to update the transmission's tuning and calibration in the future with the automaker's networked Vehicle Intelligence Platform/Global B electronic architecture. The 10-speed auto comes bolted to the 5.3-liter V8 and the 6.2-liter V8. The 3.0-liter inline-six Duramax diesel continues with the 10-speed automatic already in use. To recap the other changes for the full-sizers, we'll start with the 2022 Tahoe and Suburban, which get a new 12.3-inch digital instrument display to replace the former 8-inch unit and physical gauges. Navigation will be standard equipment displayed on the 10.2-inch infotainment touchscreen on all trims barring the base LS. Lane-keeping assist and parking sensors are also now standard, while reverse automatic braking is added to the Enhanced Display and Alert package on the top trims. Finally, the 6.2-liter V8 option is expanded to the Z71, RST and Premier trim levels, but it requires selecting one or more packages on the Z71 and RST. Moving onto the 2022 Yukon, availability of the 6.2-liter V8 expands to the AT4 trim, and the big V8 comes with a shiny pair of exhaust finishers. Redwood Metallic paint joins the exterior color palette, more wheel options are on offer, and illuminated sill plates can gussy up the rocker panels . An Enhanced Trailering Technology Package adds 13 cameras with the option for an interior accessory camera for those with enclosed haulers. On the safety side, expect reverse automatic braking to join the list of available driver assistance features. Inside, the Yukon welcomes the 12.3-inch digital cluster, the Yukon Denali welcomes the power sliding console as a standard feature instead of a $350 option.  Related Video: