Eight is Enough

In which we learn that, when it comes to the ultimate in Stingray performance, the choice may now be automatic

October 23, 2014
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I’m not this good.

The thought materializes approximately halfway into my first lap around GM’s Milford (Michigan) Road Course, a hellish gallimaufry of blind hairpins, decreasing-radius sweepers and breakfast-disgorging hillocks, all designed to push the General’s most capable performance vehicles to their limits and beyond in pursuit of short-term speed and long-term durability. For the engineers who run flat-out here every day, MRC likely packs the pulse-quickening quotient of a Mel Tormé concert. But for a neophyte like me, visions of shattered fiberglass and enduring mortification loom at every chicane.

Happily the focus of today’s evaluation, a Z51 Stingray equipped with the new-for-2015 eight-speed automatic transmission, quickly reveals itself to be a capable and forgiving coconspirator, responding faithfully to my inputs when it’s prudent to do so and tempering them to the extent necessary when it isn’t. That’s not too surprising, considering that a penchant for working in concert with the driver to optimize dynamic performance is the seventh-generation Corvette’s signature trait.

What is surprising is the degree to which the new 8L90E trans alters the character of the two-pedal ‘ray, transforming what was already a capable all-rounder into an uncompromised implement of road-course dominance. Indeed, in the laps that follow, and on a subsequent highway cruise outside Detroit, this latest self-shifter will make a compelling case for being not just a viable alternative to the seven-speed manual, but perhaps a superior one.

What’s in the box?

Given the freshness of the Stingray platform, one could be forgiven for assuming that GM’s powertrain division created the new eight-speed by simply stuffing two extra cogs into the existing 6L80E auto, expanding the case to accommodate them, and calling it good. This approach was not an option, however, due to the lack of available space in the C7’s trans tunnel as well as Team Corvette’s desire not to upset the car’s near-ideal weight balance. These design requirements forced a more comprehensive rethink of the transmission’s internal components, with impressive results.

Project engineers are justifiably proud that the 8L90E has been awarded more than two dozen patents for its innovative innards, which include four simple gearsets, a pair of open clutches and the industry’s first binary-vane pump. The latter item features two output levels, high and low, to provide an abundance of fluid flow when it’s needed, and more-economical operation when it isn’t. These efficiency improvements yield an impressive 30-percent spin-loss reduction as compared with the outgoing six-speed, meaning more of the LT1’s (or LT4’s) total output makes it to the rear wheels when you mat the go pedal.

Also from Issue 94

  • 1971 Hurricane Survivor
  • Buyer's Guide: C5
  • 1958 Roadster
  • Like-New '96 Convertible
  • LT1 vs. LT4 Comparo
  • Corvette's Near-Death Experience
  • Vintage-Vette Collection
  • Racing: C7.R Safety Features
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