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Just a general thought, with all other things being equal, a 9 speed auto vs say 6 speed auto. When cruising at 70 mph (or any speed) the 9 speed will be at a lower rpm (thus better fuel economy)?
Is this a correct assumption and is that the main reason manufacturers are coming up with these 9 to 10 gear transmissions
Just a general thought, with all other things being equal, a 9 speed auto vs say 6 speed auto. When cruising at 70 mph (or any speed) the 9 speed will be at a lower rpm (thus better fuel economy)?
Is this a correct assumption and is that the main reason manufacturers are coming up with these 9 to 10 gear transmissions
Yes the more gears the higher the fuel economy, lower engine noise and smoother ride. Downside is they make the transmission more complex, more things can go wrong and very expensive to fix.
I think Chrysler has or is working on a 8-9 speed trans, but they should first learn how to make a reliable 4 speed
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Yes, Chrysler does have a 9 speed, and it's been problematic for them. They delayed the debut of the Cherokee for several months because of shifting problems, and then required a road test on every one before shipping to the dealers. Even after final calibration the 4 cylinder only gets 22/31, slightly less than the comparable Ford Escape 1.6 with a 6 speed.
Just a general thought, with all other things being equal, a 9 speed auto vs say 6 speed auto. When cruising at 70 mph (or any speed) the 9 speed will be at a lower rpm (thus better fuel economy)?
Is this a correct assumption and is that the main reason manufacturers are coming up with these 9 to 10 gear transmissions
Engine RPM depends on transmission and drive gearing, the number of speeds doesn't have much to do with it. You could have a 5 speed that has the same ratio in 5th that a 9 speed has in 9th.
"According to Ford Motor Company’s chief engineer of transmissions, Craig Renneker, more gears give powertrain engineers more gear spread to work with. This means first gear can be shorter for better off-the-line acceleration while the top gears can be taller for better fuel economy. Having more gears allows smaller, more economical engines to power larger vehicles or improves the efficiency of existing engines."
Yes, Chrysler does have a 9 speed, and it's been problematic for them. They delayed the debut of the Cherokee for several months because of shifting problems, and then required a road test on every one before shipping to the dealers. Even after final calibration the 4 cylinder only gets 22/31, slightly less than the comparable Ford Escape 1.6 with a 6 speed.
Just a general thought, with all other things being equal, a 9 speed auto vs say 6 speed auto. When cruising at 70 mph (or any speed) the 9 speed will be at a lower rpm (thus better fuel economy)?
Is this a correct assumption and is that the main reason manufacturers are coming up with these 9 to 10 gear transmissions
The RPM at highway speed isn't necessarily lower with a 9 speed vs. 6 speed. It would be easy for the manufacturer to choose gear ratios for highway speeds no matter how many speeds in the transmission.
More speeds help the transmission keep the engine in an optimal RPM range. By shifting more frequently the engine spends less time out of its best RPM range. CVT transmissions have an essentially infinite number of speeds.
Eventually they will arrive at the continuously variable ratio transmission like the one in my 650 cc scooter. It effectively has an infinite number of gear ratios. I like it because it allows the clutch lever to be replaced with the rear brake and all I have to do to control speed and acceleration is twist the throttle.
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