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Originally Posted by pete c
I think 6 or 7 gears on a smaller engine is about all that will add performance. And the 7 speed on the new vette? That monster of an engine pulls like a freight train pretty much through its revs. As you say, give it 5 close ratios for hauling ass up to very illegal speeds and a 6th for putting along on the freeway.
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Your reasoning is a bit flawed IMO. A smaller engine needs less gears, because it has less power and lower top speed. A bigger engine needs more gears to be efficient. The Corvette's truck-like powerband doesn't benefit as much from super close gears when revving out to the limiter, but having 30% gaps between gears will definitely make a car slower, and it will also make you stay in low gears longer when driving at low speeds, which is inefficient.
7 speed gearboxes are more work to shift through, but it's worth it if it means being able to fully exploit a performance engine AND cruise on the freeway at low rpm. You don't even need Corvette level power to see the benefits; Porsche's 6 speed 3.4L cars will reach their top speed of ~180mph in 6th gear, and 6 gears to get to 180 makes for super tall gearing around town already; they will do 80mph in 2nd gear and 50 in 1st.
I would say that having 7 speeds available would be nice for a lot of cars, but 6 does fine most of the time. If you are always doing eco style driving, then a wide ratio 6 speed works just fine, but closer ratios are fun and an extra gear lets you have that as well as a nice tall cruise gear.