GM 9-speed automatic (!!!)

Saw this, thought some folks would find it interesting:

http://www.todaysmotorvehicles.com/article/chevy-gm-9-speed-transmission-120816/

Allows designers to optimize motor operation over a narrower RPM band, reduces compromises.

At what point does the gear ratio resolution not turn into a CVT?

Ford already has a 10spd auto behind the HO 3.5 ecoturd in the F150.

And all they do is add another compounder/OD unit and turn it on and off for the extra gears.... So it's not like they are really changing anything.

Ford and GM have combined efforts on both the 9 and 10 speed automatic transmissions. There will reportedly be subtle differences between the two brands' offerings, but the "guts" are the same. Weird seeing parts with both logos on them, but they are out there.

Camaros and Mustangs will soon have the same 10 speed autos.

In reply to STM317:

Sounds fair, they used to have the same 5-speed manuals. Not sure if they ever put T10s in the Mustang or if that was before their time.

What's the point of so many gears in a vehicle car?

yupididit wrote: What's the point of so many gears in a vehicle car?

Keep engine in optimal rpm range.

The charger has an 8 speed, it shifts nice and when easily accelerating it keeps the rpm at 2000-2500 while running up through the gears

It allows the engine to be designed to be efficient in a narrower range, too.

Anecdote I like is the Corvette kept the 4 speed auto for a long time because it actually got better economy. The engine's efficiency band was so broad that having more/closer ratios didn't overcome the additional weight and friction of the transmission. But Europe wanted a 6 speed so they worked very hard to make the 6 speed as efficient as the 4 speed.

I'd imagine the newer engines sacrifice broadness for narrow efficiency peaks.

The 8 speed in my Grand Cherokee has been great.

I remember one of the early Explorers we had at work seemed to have an endless supply of speeds. It just kept on shifting.

NOHOME wrote: At what point does the gear ratio resolution not turn into a CVT?

The problem with CVT's are they are not quite strong enough, yet. Good for small engines and small cars, not so good for big ones.

Is there a positive displacement CVT or do all of them still rely on friction?

RossD wrote: The 8 speed in my Grand Cherokee has been great.

Came to post this, the 8spd in my Grand Cherokee is much more pleasant to tow with than my fathers 5spd pickup with the same engine. there are many times the Jeep will shift down to 6th or 7th on a smaller incline that would cause the truck to drop to 4th and zing the rev's quite a bit higher than needed given the severity of the hill.

That's cute, but will it last as long as a TH400?

NOHOME wrote: At what point does the gear ratio resolution not turn into a CVT?

When it starts sucking ass like a CVT.

Besides: bring back the Power Glide.

RossD wrote: Is there a positive displacement CVT or do all of them still rely on friction?

If you can invent infinitely variable teeth.

Technically ALL transmissions rely on friction, barring some racing weirdities like spline clutches or 2-speed transmissions with the clutch on the countershaft.

My 200c has a 9speed. No issues.

It even has a turny knobby instead of a stick. Flappy paddles too but I never use them.

Got it, thanks!

I just realized that a "positive displacement CVT" is possible if you have a variable displacement hydraulic pump (swashplate style, like A/C compressors) and a fixed displacement hydraulic motor. I don't know how efficient, or reliable, hydraulic power transfer is relative to the fairly well proven push-chain setup that CVTs use.

I realize that RossD meant engagement instead of displacement, but that got the ol' brain working.

The ZL1 that just set the time at the 'Ring had a 10spd auto.ZL1 Nurburgring lap

Knurled wrote: I just realized that a "positive displacement CVT" is possible if you have a variable displacement hydraulic pump (swashplate style, like A/C compressors) and a fixed displacement hydraulic motor. I don't know how efficient, or reliable, hydraulic power transfer is relative to the fairly well proven push-chain setup that CVTs use.

I think that's how a lawnmower hydrostatic transmission works, the "shifter" just adjusts the swashplate angle.

In reply to akamcfly:

Eww. Shifting via a "little twisty knob" strikes me (viscerally) as kinda gross.

I enjoy resting my hand on the gear lever. I want a mechanical connection to my vehicle. The "little twisty knob" will work when the whole process is automated in our self driving pods, but for now I feel like we should stay connected to the driving process.

BrokenYugo wrote:

Knurled wrote: I just realized that a "positive displacement CVT" is possible if you have a variable displacement hydraulic pump (swashplate style, like A/C compressors) and a fixed displacement hydraulic motor. I don't know how efficient, or reliable, hydraulic power transfer is relative to the fairly well proven push-chain setup that CVTs use.

I think that's how a lawnmower hydrostatic transmission works, the "shifter" just adjusts the swashplate angle.

That's how any variable displacement hydraulic system works. I think most lawnmower hydrostatics are fixed displacement, which means that you've got a gear pump driven off the engine at all times that simply recirculates back to the tank until you move the spool valve one way or the other to send flow to the motor. (Fixed displacement = always produces X liters of flow per revolution, variable displacement will be anywhere between 0 and some maximum Y liters of flow per revolution depending on plate position). The spool valve allows you to divide flow between recirc to the tank and sending it to the motor up until full valve shift (max speed) so that all flow goes to the motor. At this point, the only limiter is the relief valve to prevent overpressure. Fixed displacement hydraulics are much, much cheaper than variable displacement, and are much simpler to control. Some of the expensive stuff may use variable displacement though.

Hydraulics can be efficient in that a very high percentage of flow directly produces movement, however high pressure and long tubes with high flow rates result in a lot of wall friction in the hoses (a lot of lost heat). i.e., it works well for low speed stuff, but not so much for high speed. It could be done though. Many tractors and construction equipment run exactly as you propose.