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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.

GMC Syclone pickup returns via Special Vehicle Engineering

The original GMC Syclone was a 1991 mid-size Sonoma pickup turned muscle truck. Its heavily modified 4.3-liter V6 sported a turbocharger, intercooler, and modified internals, raising output to a Corvette-baiting 280 horsepower and 350 pound-feet of torque. The engine was paired with a four-speed automatic, rear-biased all-wheel drive, and four-wheel antilock brakes (the coming thing). With an all-black livery and a lowered ride height, the Syclone looked the business, and backed up those looks with a 0-to-60 time of 4.3 seconds and a 13.4-second quarter-mile, according to contemporary magazine testing. Given all the recent interest in high-performance pickups, it's amazing that GMC hasn't revived the Syclone. But where manufacturers leave an opening, the aftermarket steps in — in this case that's Specialty Vehicle Engineering, which as CNET reports is resurrecting the nameplate for a build of 100 new Syclones, based on the GMC Canyon, which will update the idea a lot more horsepower. The 2019 Syclone takes as its starting point the extended-cab version of the Canyon. The engine is again a V6, this time a 3.6-liter fitted with a supercharger and a custom cat-back exhaust system, upping output to 455 ponies from the stock 306. SVE's Syclone can be had with rear- or all-wheel drive, and it, too, features upgrades to the brakes and chassis. Six-piston front calipers are fitted in place of the standard four-piston units, and the slotted front rotors are upsized from 12.2 inches to 13.6. The suspension is lowered by two inches up front and five inches at the rear, with stiffer traction bars, bushings, dampers, and a heftier rear anti-roll bar. Unlike the original, the modern Syclone can be had in colors other than black — any of the standard Canyon hues are available — but the appearance is customized with rocker-panel extensions, body-color grille and rear bumper, and a composite hood insert. The interior gets embroidered logos and badges, including a numbered plaque on the dash. The price for the Syclone is $39,995 — that's for the package, on top of the cost of the truck. But at least ordering is easy: The Syclone package can be ordered through select GMC dealers.

'Killing a Duramax' Gale Banks YouTube series methodically tunes a diesel to death

Learning or perfecting a skill by watching YouTube videos is known as attending YouTube University. GM Authority picked up on one of the video site's more fascinating courses, hosted by Gale Banks; in a fair world, he should be referred to as Professor Banks when it comes to diesel engines and truck tuning. A few months after GM introduced the updated L5P 6.6-liter Duramax diesel V8 in the 2020 Chevrolet Silverado HD and GMC Sierra HD that ships with 454 horsepower and 910 pound-feet of torque, Banks decided he wanted to methodically tune the engine to death. The purpose of the resulting series, called "Killing a Duramax," is to push more power out of the engine in order to discover which parts break and when — or, as Banks puts it, force-feed the Duramax "until the crank hits the street and the heads hit the hood." With that knowledge, Banks can figure out all the weak points on his way to building what he calls a "Superturbo," that being a supercharged, twin-turbo race engine with more than 1,000 hp. What makes the series fascinating is Banks' knowledge, paired with the company's comprehensive iDash engine monitoring system that keeps tabs on a glut of parameters every step of the way. So for instance, you get Banks explaining the differences between inches of mercury and barometric pressure, how those are different from the water content of the air measured in grains, then showing those readouts on the iDash, then explaining in detail how they affect the air density in the Duramax system. The stock Borg-Warner variable turbo gets a lot of airtime — Banks accuses it of being "out to lunch" because he feels it's the weakest link on the engine. That turns into a turbo teardown and a deep explanation of performance pitfalls, such as when air pressure on the turbine begins to diverge from the boost pressure coming from the compressor. Banks says he can keep close tabs on where power's coming from, because the iDash monitors the horsepower contribution provided by the ambient air, the turbo, and the intercooler separately. The major changes so far are a stouter Precision 7675 turbo and TurboSmart wastegate (episode 5), a twin intake (episode 6), a custom liquid-cooled intercooler from a marine engine, a new GM oil cooler and synthetic oil (episode 10), and new injectors (episode 11).