New info on the automatic transmission// Addendum

[ciddyguy]

Hey,

I've done some Googling and researching of this new automatic being offered in the 500. What I knew is that it uses a Lepelletier gear set, which uses 2 other types of gear sets, a 5 pinion Planetary gear set and Ravignaux gear set to allow for a very, very compact 6spd automatic that literally fits in the same space as a typical 5spd manual gearbox.

Aisan Reiki, ZF, and others are making variations of this automatic, along with dual clutch versions etc and it DOES look like they are moving away from using a traditional torque converter as the best I can gather, this new Lepelletier set up uses what appears to be 5 discreet clutches in a clutch to clutch actuation whereby one clutch disengages while another engages and the clue is when you stop at a light, all of the clutches disengage the transmission from the engine, even if the shift lever is still in D to reduce internal temperature due to friction while stopped. Now, those who work in the transmission business uses clutches as a nomenclature so they may actually mean the clutches within the torque converter but it may well be actual clutches, similar to what is found in a manual, the images I see does not show what looks to be a normal torque converter at the bell housing end of the transmission.

A version of this transmission was/is used on the BMW 7 series, I think as far back as 2001 according to one article, which is talking about the very model to be used in that car. Over on Wikipedia, they list this model from Aisin, the AWTF-80 SC used in the transverse FWD setup, which may be similar to the one used in the Fiat and due to its size and how it's made, the whole unit weighs in less than 200# and uses fewer parts for more reliability and the Transmission Control Unit (TCM) is housed inside the transmission for better reliability and for longevity to boot. The article can be found, here 

One thing in even MORE research found that the Ravignaux gear set has clutches as part of the gear set, not a clutch like in a manual, but rather, geared clutches that depending on which one or ones locked, usually via a brake, determines which gear you are in, or reverse for that matter but apparently the coupling is STILL a torque converter between it and the motor.

Here are 2 videos demonstrating the Ravignaux gear set in the Toyota Camry 6spd transmission, the first is how they all go together, the second is how it functions, but the torque coupling is still the fluid bound TC, at least in many versions, and I'm now suspecting the same for the Aisin unit in the 500, but with the use of a lock up feature for I think 5th and 6th gears for cruising to reduce slippage losses.

Video #1

Video #2

So in a sense, it's a very, very compact conventional transmission but still would like to know if this is the permanent automatic offering or will this be supplanted by a dual dry clutch at a later date, say with the new refreshed 500 for 2013.

[cinquecento]

Good work!
Sounds like at the very least this is going to be a really top-notch slushbox, and at best some sort of dual-clutch system.  I've never heard of a transmission with 5 clutches, but if it's both compact and light, the more the merrier!  

[FiatGal]

ciddyguy wrote

...
 one clutch disengages while another engages and the clue is when you stop at a light, all of the clutches disengage the transmission from the engine, even if the shift lever is still in D to reduce internal temperature due to friction while stopped.
...
here 

With my limited knowledge of mechanics, I can't help reading that and wondering how this would handle in snow/ice.  I know that in my, granted, old car with old manual gear box, if I disengage the gears coming to a stop, I skid.

Obviously, there's something I'm missing, since plenty of folks drive automatics, and there aren't huge pile-ups everywhere...

[ciddyguy]

LauraInME wrote

ciddyguy wrote

...
 one clutch disengages while another engages and the clue is when you stop at a light, all of the clutches disengage the transmission from the engine, even if the shift lever is still in D to reduce internal temperature due to friction while stopped.
...
here 

With my limited knowledge of mechanics, I can't help reading that and wondering how this would handle in snow/ice.  I know that in my, granted, old car with old manual gear box, if I disengage the gears coming to a stop, I skid.

Obviously, there's something I'm missing, since plenty of folks drive automatics, and there aren't huge pile-ups everywhere...

Laura, if your old car didn't have ABS, then yes, the likely hood of it skidding is greater, with ABS, you should not have skidding issues when you disengage the clutch.

When we had a major snow here in Seattle in Dec of 2008, I had to drive in the stuff in a 92 Ford Ranger with manual and rear wheel ABS only on a 2WD truck and was able to keep the truck from skidding and such while slowly traversing mild incline, downhill to get to the freeway from within the city as our Mayor at the time refused to clear the city streets, causing mayhem and pissed off drivers and Metro, our bus system, over half of their fleet was out of service due to being stranded on the streets as a result and you don't want to fully apply the brakes except at the very last moment, but use it and your engine as braking by keeping the transmission in first or second gear and just let it keep you from going fast, using your brakes gently as an aid and you should do fine.

[ciddyguy]

cinquecento wrote

Good work!
Sounds like at the very least this is going to be a really top-notch slushbox, and at best some sort of dual-clutch system.  I've never heard of a transmission with 5 clutches, but if it's both compact and light, the more the merrier!  

Thanks.

BTW, I managed to read a bit further on the torque converter itself and what I read makes me think more and more this autobox in the Fiat uses actual discreet clutches because of the diagram I posted yesterday shows variations of those clutches engaging or disengaging depending on the gear used. A torque converter uses 3 elements at a minimum, a pump, a turbine and a stator, the stator sits between the other two and varies oil pressure, which is how a torque converter works by fluid coupling, the stator simply allows for multiplied torque, of which the pump and turbine can't do on its own. A lock converter simply locks the TC at cruising speed, reducing slippage, which is where inefficiency comes into play with most older automatics.

[trinME]

To Laura, and others wondering about the interest in the internal workings of the auto transmission-
The question is whether it is a conventional design,with a hydraulic torque converter, or a newer design, which maintains a direct mechanical connection between the engine and the drive wheels. A torque converter loses a significant amount of energy to heat. The newer designs are much more efficient.
The result being that, while a conventional auto transmission results in less power and fuel economy than a manual transmission, the newer designs can be even better than a standard.
Thanks, ciddyguy, for pursuing this.
-TR

[ciddyguy]

trinME wrote

To Laura, and others wondering about the interest in the internal workings of the auto transmission-
The question is whether it is a conventional design,with a hydraulic torque converter, or a newer design, which maintains a direct mechanical connection between the engine and the drive wheels. A torque converter loses a significant amount of energy to heat. The newer designs are much more efficient.
The result being that, while a conventional auto transmission results in less power and fuel economy than a manual transmission, the newer designs can be even better than a standard.
Thanks, ciddyguy, for pursuing this.
-TR

Yer quite welcome! :-)

[FiatGal]

Thanks for that TR. I was rereading all Chris's posts on dualogic, dual dry clutch, etc. Still do not get all the specifics, but it helps to see the bigger picture.

I know this is frivolous, especially when the bigger picture is a better car, but I really like the sporty shift handle...

[Fiat500USA]

ciddyguy,

This is excellent information and I thank you for sharing it with everyone here. It's a great overview on this trans. I'm still waiting to see if I get confirmation that this is the trans, but I think everything points to it.

Thanks!
Chris

[Gerre]

Okay. Have NO idea what any of this means, but it made me think back to my 1964 500D. Four speed manual, NO synchromesh in first gear and not much more in the other gears !!! i.e., the only way to change gear was to double-declutch. For all you youngins out there ... 1) Clutch in, 2) gear level into neutral, 3) Clutch out, 4) Clutch back in, 5) gear into next position, 6) Clutch out. Yup. Every time that you changed gear. I started driving lessons in the UK after leaving Africa and I got my leg slapped hard by the instructor every time I double-declutch. It was firm habit by then. The worst was when you were about to come to a stop and the traffic light suddenly changed to green and you had to get it into 1st gear!!! Grind, grind, grind.

[ciddyguy]

What we are talking about is the automatic transmission and trying to decipher if it uses a fluid coupling, a torque converter or an actual clutch, in this case a solenoid actuator is used to actuate the clutch so when you shift, there is no clutch pedal to deal with in an actual clutch based coupler like what VW uses.

What it looks like is the automatic offered here in the Fiat is a conventional automatic but has a sport shift feature where you nudge the lever up to downshift, down to up shift or simply leave it in drive and treat it like a traditional automatic.

What brought this on is that with a fluid based coupling of the transmission and the engine is loss of power (slippage) and potential gas mileage figures - and as not as direct a coupling (which can be felt in some cars) with the dual clutch units from VW and Ford and others using similar systems, you get a more direct coupling of transmission and engine, much like a manual and in many cases they ARE simply automated manuals, using solenoids to do the shifting and clutching for you, or let you select the gears yourself (when you shift, it's like I described above as the shifter is identical to a traditional automatic, just the mechanicals are different), but continues to use the solenoid to actuate the clutch, unlike a conventional manual where you have to do it all yourself.