Edmunds Inside Line today announced – in an unconfirmed report – that the manual transmission on the C7 Corvette will have seven speeds. The speculation seems probable to this writer. Judge for yourself:
"Inside Line has learned that the 2014 C7 Chevrolet Corvette will be available with a seven-speed manual transmission.
"Although not confirmed officially by Chevrolet, a source with knowledge of the C7 project confirmed that the upcoming Corvette will offer a seven-speed manual transmission. This comes on the heels of Porsche’s announcement that the 2012 911 would offer a seven-speed manual along with its seven-speed PDK dual-clutch automated manual gearbox.
"The next-generation Corvette is expected to use a revised version of its 16-valve pushrod V8 engine architecture. Headlining the changes are direct injection and a variable valve lift system to further enhance its already formidable performance while bolstering efficiency.
"The addition of a seven-speed manual might be viewed solely as a fuel efficiency play, but we suspect that Chevrolet will continue to use two overdrive gears like the current six-speed manual. This would allow the engineers freedom to tighten up the spacing of the lower gears for improved low-speed performance.
"Another benefit to the seven-speed manual gearbox is product rationalization — Chevy can use the same ratios for all versions of the car. Today, the ZR1 currently runs a close-ratio Tremec TR6060, while lesser Corvettes employ a different gearset."
I don’t think the current car has 2 overdrive gears, maybe one. Except in the ZR1 where the 6th gear is the top speed gear, not an overdrive gear.
The current MM6 6-Speed manual transmission, used in both 2011 and 2012 Corvettes, does indeed have two overdrive gears. The ratio for fifth gear is .74 and the ratio for sixth is .50.