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Old 10-01-2012, 11:48 PM   #18
arghx7
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Quote:
Originally Posted by HipToBeSquare View Post
9 or 10 gears?
How big of a transmission are we talking about? If it is a FWD transaxle, there is much more limited space.
How big are each of the gear sets?
are they robust enough to not wear out or shed gear teeth after years of use?
I'm sure it's a few Ravigneaux gearsets put together. The 8 speeds out right now are surprisingly more simple than you would expect. It's not like a manual transmission.

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How often is this thing going to hunt and peck for the right gear ratio, and how much time spent shifting between 9 or 10 gears?
That's a big hurdle for the calibration engineers, but the current crop of 8 speeds don't really have that problem. But at least you won't have the annoying drone found in many CVTs.

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How narrow is the engine's power band? That is the only major reason for many gear ratios. A wide power band, which the new DI & Turbocharged engines are supposed to have, should require LESS shifting, not more.
You do realize that there are teams of engineers getting paid upper middle class salaries to figure this out? And they won't post the confidential details on a car forum.
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How many bands, hydraulic circuits, and moving parts are vulnerable to failure, and trashing the rest of the gearbox? How much is a 9 or 10 gear gearbox going to cost to replace, or have rebuilt?
You do realize that modern automatic transmissions don't use bands right? Something could definitely go wrong but as others have pointed out, modern A/Ts last a long time now especially when you don't put thermal stress on them.
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My family has had all sorts of different brands of cars that have required transmission re-builds. Chrysler, Ford, GM, and Subaru. Hondas are known to have potentially delicate transmissions.
Every manufacturer has a weak link or two in their lineup. Honda has had some good ones but in the late 90s/early 2000s they had some turds.
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CVTs from all brands have reliability issues and seem to have higher repair rates after warranty expiration than automatics or manuals.
Jatco CVTs have been holding up well (chiefly Nissans, although they are used in other vehicles).

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I don't trust efforts to introduce more complexity, and more un-proven parts, when they have yet to prove definitively that the transmissions are rock solid.
That's what durability testing is for. It doesn't catch everything though. The complexity is there due to customer demands for improved fuel economy and acceleration, plus tightening government standards. That's why powertrains have been changing so fast lately.

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What brand is known for transmissions that *DON'T* need repairs beyond the regular maintenance fluid change service, and are more than capable of coping with any driving style, and any amount of power than the engines put through it.
It's hard to say for cars that have been around for only a few years, but my '99 Corolla with 4 speed AT has 222300 miles on it currently. Off the top of my head I think Aisin makes it but I'm not sure.
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