2008 Gmc Yukon Xl 1500 Denali on 2040-cars

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GM's fullsize SUVs boost highway mileage by nearly 10 percent

We met the redesigned 2015 versions of the Chevrolet Suburban and Tahoe, and the GMC Yukon and Yukon XL at the 2013 LA Auto Show. Improved gas mileage numbers have been announced to go along with the improved exteriors and interiors, with city mileage improving by seven percent and highway mileage going up by nearly ten percent; you'll now get 16 miles per gallon in the city and 23 on the highway.
The only applies to models with the 5.3-liter engine, though, not the premium Yukon Denali and Yukon XL Denali SUVs with the 6.2-liter motor. Still, the 5.3 gets you more power than previously, with 355 horsepower and 383 pound-feet of torque underfoot, on top of the improved fuel economy numbers. The 6.2-liter sticks with official mpg ratings of 15 highway, 21 city. There's a brief press release below with words straight from the horse's mouth.

GM also sheds parts from its pickups to boost payload ratings

The row between Ford and Ram over who boasts the best-in-class tow rating for heavy duty pickups has revealed a number of things. Chief among them is a report that Ford removes items like the spare tire, jack, radio and center console from its vehicles in a bid to lower its base curb weight and therefore keep the truck's gross vehicle weight rating down.
For those that need a refresher, GVWR is the vehicle's curb weight plus its maximum payload. A lower GVWR allows Ford to station its F-450 among the so-called Class III pickups, despite the fact that internally, it has the makings of a more brutish Class IV truck.
Ford explains away these deletions, saying a customer could order their vehicle in such a manner. It has also come to light that Ford is not the only automaker to engage in such practices.

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.