So How Many Gears Are Enough In An Automatic Transmission?

As long as performance and economy is improving it's never too much.

It would be interesting to see a weight comparison. Eventually you would reach an optimum number of gears before the weigh gains on the car outweigh the fuel economy gains.

More gears===>greater complexities===>higher reliability issues===>angry car owner. My .02 pesos, 5 speeds is all you need.

Actually I'd question when does there becoming a diminishing return between a large number of selectable gears and a CVT transmission?

A very good question, bragging rights,lol I would like to see the numbers on 0-60 and fuel economy numbers to determine what the optimum number of gears would perform best, tranny rebuilds would be more $$ with more gears, do you all remember the 3 speed? I had one in my highly modifies 1976 Bronco, the monster truck builder who built Big Foot built my truck, (it was too high)

i agree 100%. 6 gears are perfectly fine.

Lots of stupid comments here from so-called "automotive engineers", eh?

This transmission will most likely be geared towards fuel economy rather than outright performance. And I've never had a problem with a 7 or 8 speed automatic because these transmissions, if properly tuned, can reduce fuel consumption while improving performance.

I have never had a problem with a 7 or 8 speed either,lol All I have is a 5 speed, ok I am being a smart axec,lol But another point i would throw in there,is, with the extra expense of a 9 speed and the extra cost of the tranny,and the cost of a rebuild would it pay for its self with the extra savings in gas?

You just have to make them out of a new lighter material

If the fuel economy is significant during normal driving, i'm all for it. I would not like to lose much in the performance area though.

I think the answer is 9 - I've read a few articles that suggest anything beyond 9 speeds is too heavy and/or expensive to be practical.

If we estimate that each gear can be optimized for a 500-800 RPM range, and if we assume that engines have a practical RPM range between 800 RPM and 6000 RPM, 9 different gear ratios should cover the practical RPMs available with room to spare.

As others have said, it all depends on how the math shakes out...but I think 9 is the answer for most vehicles.

nEIN 9 nEIN 9 nEIN 9

i had a lexus is-f for a year, at high speeds in 8th gear on the hiway i got 25mpg, i think thats very impressive however in city driving, the transmission drove me nuts as it really is always hunting for the proper gear...
i have a dct M3 now and with 7 speeds i think its perfect..

The number of gears depends on how the car is designed to operate.

Fuel Economy - CVT
Luxury/Sport w/ big HP - 7 Speed
Economy/Daily Driver - 6 Speed
Sport big engine - 7 Speed
Sport small engine - 6 Speed
Electric - ?