Needs a torque convertor for for the AFM? I don't get that. Is that because they plan to run the convertor unlocked while using cylinder deactivation? At least under loading that is (instead of downshifting and/or activating more cylinders, bump engine speed slightly by unlocking the convertor). I tend to think of convertor slippage as simply waste, so that strikes me as counter-productive. Or is it to dampen vibration--perhaps at heavier loading the V4 shakes more, and by using the extra mass of the convertor (and perhaps some slippage too) they can dampen it out. ?
The 8L90 transmission matches the Corvette’s outgoing 6L80 6-speed unit at 24 ins. (598 mm) long but drops 9 lbs. (4 kg), using advanced lightweight materials such as magnesium and aluminum on a number of parts. Coupled with a unique design, which in an industry-first includes an off-axis oil pump, the work resulted in 24 new patents. Working in tandem with cylinder deactivation, a feature GM calls Active Fuel Management, the 8-speed provides a 3.5% bump in Corvette fuel economy to as much as 29 mpg (8.1 L/100 km) highway, according to EPA estimates. It’s rated at 16 mpg city (14.7 L/100 km). GM needs a transmission with a torque converter to wring out all the benefit of AFM, another reason to avoid a DCT, Juechter says. “That lets us be more aggressive in AFM, and that’s very important because AFM is the single biggest card we can play in terms of fuel economy.”