We haven't overpowered our '06 Corvette's factory clutch quite yet-but when you're testing, tuning, and otherwise driving the hell out of your C6 project car, the best approach to remedying a near-inevitable case of the slips is a proactive one. Our power output thus far has been increased by a 3-inch CORSA exhaust, VaraRam induction items, and a set of long-tube ARH headers, to the tune of about 33 rear-wheel horsepower overall. But with much more to come, it's only a matter of time before the factory LS2 clutch becomes a liability.
A call to late-model GM clutch specialist Spec yielded one of the company's Super Twin units. The main idea behind two clutch discs is that they yield increased frictional surface area, which improves holding ability. While the torque rating of any of the models in the Spec Super Twin line is greater than our LS2 will likely ever make, it's nice to know that the extra capacity is there. Moreover, the additional surface area of twin-disc clutch systems simultaneously allows the use of a far less aggressive friction compound than is needed for an equivalently rated single-disc unit (not to mention a lighter pedal effort requirement), which is a boon for driveability. Spec sells the only twin on the market that features all-billet construction, allowing for lighter weight and a 0.001 machine tolerance. There's also a sprung hub for smooth engagement and 1050 high-carbon steel friction surfaces for tremendous wear life and warp resistance.
While pricier than the GM LS7 clutch (a common upgrade that can handle more horsepower than a stock LS2 clutch), the Super Twin gives us an actual advantage over the Z06 clutch system. Plus, it's fully rebuildable, with kits ranging from $199.00 to $599.00 on our particular unit. This shouldn't be an immediate worry by any stretch, though, as Spec says that its first prototype (a "trim 3," versus our trim 1 unit) is still working great, despite close to 300 10-second strip passes and nearly 30,000 street miles. They're still not sure how long these suckers can last! As we're a bit short on time and space this issue, we'll give you the lowdown on how this clutch drives (and races!) in our next C6 project installment.
As clutch replacement requires removal of almost the entire drivetrain, we figured there was no better time to strengthen our transaxle. See the sidebar for details on our DTE Differential Strut. G
Bracing for Breakage (Prevention, that is!)Aside from the usual breed of parts destruction you might expect from an IRS-equipped vehicle (like axleshaft and CV joint breakage), some high-power C6 owners have found out the hard way that their Corvette's transaxle assembly itself can fail. Think of the physics of the situation: torque is naturally imparted to the diff under acceleration, which creates a separating force between the upper mating surfaces of the diff and transmission. Given an engine with enough horsepower, this torque could overwhelm the structure of the factory transaxle assembly, particularly on a hard shift. Imagine a twig snapping and you get the idea.
DynoTech Engineering Inc. has created a solution. The company's Differential Strut Kit is advertised as significantly increasing the strength of the differential and transmission assembly for high-performance use. According to DTE, this differential strut increases the overall strength and rigidity of the diff/trans assembly, and does so by diverting drivetrain stress to the strongest points of attachment on the C6 transaxle.
Follow along while we install DTE's Differential Strut Kit onto our C6's transaxle, readying ourselves for hard launches and shifts with reduced fears of breakage. While we're obviously doing the install with the transaxle out of the car, DTE says that this item can also be installed without transaxle removal (you just have to lower the rear subframe slightly to gain sufficient clearance).