[dark.knight]

VW has decided to stop any further development of a 10-speed DSG which was in the works. This maybe only for the time-being though as the continuous pressure on emissions and fuel conservation has companies working overtime on transmissions & engines.

The main reason here could be that the 7-speed DSG itself is quite sufficient for the engines ranging from 1.2-1.8L. The DSG's were already noted for a range of problems varying from engine judder to overheating gearbox & acceleration issues, most reported from their key markets China, Europe & India. With the 10 speed DSG they wanted to shoe-horn 2 gears into the early RPM's to improve pick-up and the one into the higher for efficiency.

The question here is where does the diminishing returns start? I'd say a 7-speed for now if tuned smoothly & reliably can easily do a great job. In varying traffic conditions with 10 to pick from the computer will only be hunting for gears to maximise efficiency which may not align with what the driver is trying to do thus inviting more problems. It does bode well with marketing & catching the buyer's fancy and anybody can ask what's wrong with more gears, why not what's wrong with just the right number of gears?

http://www.motorauthority.com/news/1...mission-report

[GTO]

Echoing what ZF stated 3 years ago:

Now, Automotive News Europe quotes ZF CEO Stefan Sommer as saying nine speeds are the “natural limit.” In Sommer’s words, “There is no hard line, but you have to consider the law of diminishing returns. The question is whether adding even more gears makes sense.”

That sentiment is echoed by Julio Caspari, president of ZF’s North American division, who believes that the race for more gears is driven by marketing and not engineering. As proof, Caspari says that there’s only an 11-percent gap in efficiency between today’s most-efficient gearboxes and a theoretically perfect ideal.

Source. And a related article.

Originally Posted by dark.knight

I'd say a 7-speed for now if tuned smoothly & reliably can easily do a great job.

Agreed.

Additional point from my 530d review:

Originally Posted by GTO

You now know why these big cars are getting 8 speed gearboxes. They need the super tall 7th & 8th ratios to deliver fuel efficiency that doesn't shock you. With a 6-speed gearbox, highway fuel economy would probably be in the single digits, earning them the reputation of gas guzzlers.

[hybridpetrol]

Originally Posted by dark.knight

It does bode well with marketing & catching the buyer's fancy and anybody can ask what's wrong with more gears, why not what's wrong with just the right number of gears?

If there are 10 gears in manual transmission, no one would ask what is wrong in having these number of gears! As it is, 4th gear and above can only be used if the road is relatively free, and in city traffic, it is a rare thing.
Since it is automatic, more gears (>5) are seen as an additional advantage, especially for mileage.
But if the number of gears become too many, won't it function somewhat similar to CVT?

[sgiitk]

Is not a 10 speed box too close to a CVT!! Might s well go to a CVT.

[dark.knight]

Originally Posted by GTO

You now know why these big cars are getting 8 speed gearboxes. They need the super tall 7th & 8th ratios to deliver fuel efficiency that doesn't shock you. With a 6-speed gearbox, highway fuel economy would probably be in the single digits, earning them the reputation of gas guzzlers

Absolutely, for machines having well in excess of 2L engines, a gearbox with 8 gears or more will be very useful in reducing effort at the top end and it'd result in better economy as well. No hard & fast rule though as it can apply to smaller engines too, but the real problem is the cost in producing an 8+ speed DSG for VW would price already expensive cars one peg higher & that has got them worried. In a 40+ lakh rupee car an insignificant price rise of 1 or 2 lakh for a better gearbox might tempt buyers in that range all the more due to better drivability & technology but when that same price rise is applied to a 10 lakh Polo Tsi or Vento then that would eliminate a substantial portion of buyers from considering it. The potential efficiency gains would be only numbers as it depends on whether the driving is such that the engine will at all reach gear 10. That's where real world diminishing returns vs cost comes in. As you've posted if the gap of efficiency between ideal & reality is 11% then to the end consumer breaking-even wouldn't even seem worth the time.

Originally Posted by hybridpetrol

If there are 10 gears in manual transmission, no one would ask what is wrong in having these number of gears! As it is, 4th gear and above can only be used if the road is relatively free, and in city traffic, it is a rare thing.

The problem today is everyone wants a car with F1 prowess & technology on commuter roads, with the fuel efficiency of a small hatchback & aerodynamics of super-cars. While car technology has progressed on all fronts, the 3 key factors i.e power output, gearing & fuel efficiency will each change upon change of 1 factor, for eg. power output increase may decrease F.E but better gearing will increase F.E but affect power at that particular gearing band etc. Ultimately manufacturers will have to sell to the majority buyer preferences & that's where value & balance play their bit.

[theMAG]

Not surprising from any quarter. Considering the current 9-speed ZF boxes have been plagued with usability issues on vehicles such as the Jeep Cherokee, Acura TLX and Chrysler 200, adding another gear without addressing these issues would have defied logic and essentally not having met its original goals.