On Jan 24, 2:33*pm, Ashton Crusher > wrote:
> On Fri, 20 Jan 2012 05:47:04 -0800 (PST), "
>
> > wrote:
> >Lexus and Hyundai currently have 8. *Dodge will soon have 9. *Now
> >seems Hyundai is upping the ante and developing a 10-speed automatic
> >transmission. *Good god, where does this end? *Soon cars will be
> >sporting enough gears to make a trucker blush.

> I suspect a lot of it is marketing. *Once you add a third planetary
> gear set you have all sorts of possible ratios. *Now that most
> transmissions are controlled electronically rather then by simple
> hydraulic valves, it's almost trivial to add another "gear". *I read
> some years back that in many of these transmissions they often
> "skipped" one or more of the possible ratios depending on how hard you
> were accelerating since most of the time you don't need all of them to
> move things along. *It would be interesting to talk to a car makers
> autobox engineer about this.

I'm sure skipping would have to happen quite often. If you're putting
your foot in it, you're not concerned about economy, you want
acceleration, so it would make little sense to hit all the gears. But
if you're cruising, the trans should then act to keep the engine in
it's sweet spot for best MPG. Or so it seems.

Patrick