Short answer, yes. If the motor has sufficient torque/weight then cars drive just fine with six speeds. Are you getting then ultimate in terms of fuel consumption is something I cannot answer.
Depends. In my experience, most of the 8-speed transmissions just use six more tightly spaced gears for normal driving and two overdrive gears for highway speeds. There are advantages and disadvantages just like anything else, and there can also be good or poor applications. My opinion is that although we're seeing an arms race in gear count, anything more than 8 or 9 is going to see returns that diminish very quickly, as well being harder and more expensive to design and manufacture. Add that more and more vehicles are using turbocharging to broaden their power-bands, and we'll this craze die down.
The Japanese brands, for some reason or other, are always behind the curve a bit with regards to transmission technology - I don't know why. Seemingly they want to perfect yesterday's technology, and they do that really well...most reviews you see stress that Honda for example does a really good job with five speeds in the Civic and CR-V automatics, but they're still only 5 speeds, and Hondas don't have a notably wide power band to begin with. Subaru up until very recently had 4-speed automatics and the Corolla still comes with a 4-speed auto (not that Corollas are setting the world on fire anywhere but rental lots).
It's not really just the 8 gears, it's the "step" between the gears and the overall gear spread that's important. ZF has publicly stated themselves that 8 or 9 speeds is about as far as it goes. I still have trouble wrapping my head around the different clutch engagements and planetary gearsets, but needless to say their transmission is definitely a benchmark, not only being extremely versatile (used from trucks to sports cars with different calibrations for shift speeds and smoothness) and has had a huge impact on the character of the cars they're in. In the case of Chrysler, you can arguably say it's partially what turned them into a true competitor practically overnight.
The problem/reason why Honda is gun-shy about new transmissions is because of their (relatively infamous) V6 transmission issues from back around 2000, coupled with the fact that for the most part they have their own unique designs from other manufacturers. Recently they seem to be favouring the CVT route.
I've had my GS350 for over 20,000 miles now and my six speed tranny has never been a problem. There are a lot of two lane black tops around here with 55 mph speed limits and folks who love to drive them at 45. Flooring the GS to get around these slowpokes unleashes unbelieveable power immediately. I wouldn't drop an 8-speed into what I have because, as they say, "if it ain't broke, don't fix it!" Shine on, Dr.John
How many gears you need depends on powerband. Years ago I had a Jeep that did okay with a 4 speed auto. Its 4.0L inline 6 engine made gobs of torque starting down low and had a broad peak, so widely spaced gear ratios suited it just fine. 4th speed was tall enough enough to cruise at 75 at just a bit over 2500 rpm. Our other car at the time had a small engine and a 5 speed manual. The ratios were closer together to keep the engine on boil, and as a result 5th was too short for comfortable cruising on open roads. At 75mph the engine was screaming at nearly 4000 rpm. It would have benefited from a 6th gear.
That's just an ignorant remark worthy of your name. Lexus was the first to bring an 8-speed to market w/ the LS in 2007. Obviously they are saving the 8-speed for a V8 GS-F.
Comments
The problem/reason why Honda is gun-shy about new transmissions is because of their (relatively infamous) V6 transmission issues from back around 2000, coupled with the fact that for the most part they have their own unique designs from other manufacturers. Recently they seem to be favouring the CVT route.
If you have a small peaky, low torque engine, then 8 is probably better.
Shine on,
Dr.John
That's just an ignorant remark worthy of your name. Lexus was the first to bring an 8-speed to market w/ the LS in 2007. Obviously they are saving the 8-speed for a V8 GS-F.