Naming problem (hydraulic transmissions)

[gerhardf]

Hello all,

I've got a problem with naming of hydraulic transmissions. This is in the context of a manual for an aftermarket item that works with both automatic and manual hydraulic transmissions (or maybe better, what I call "automatic and manual hydraulic transmissions" -- see below). I usually write most of our documents, even though I'm neither a transmission guy nor a native English speaker. Usually, it works out just fine, but with this we're not quite clear about the correct terms.

What I call an automatic transmission is a transmission that shifts automatically, and in the same vein a transmission that does not do that I call a manual transmission. (Of course there are cases where that is determined more by the controller rather than the transmission, but I'll stick with the simple things for now.) For me, a hydraulic transmission is a transmission that uses hydraulics to control gear positions. I'm not sure I'm correct with either of these, but just so that you understand what I'm talking about.

I started out talking about exactly what I wrote above: automatic and manual hydraulic transmissions. But my tech guys tell me that when I talk about manual hydraulic transmissions, people might not really know what I'm talking about, because the term "manual" in this context is too strongly associated with the H-pattern type manual transmissions.

Additionally, to muddy the waters still more, one of the manufacturers of such a manual hydraulic transmission, McMillin Racing, call their M1 transmission an "automatic transaxle", even though I'd call it a manual hydraulic transmission (or transaxle, but I think this doesn't matter in this context).

Can you guys please help me out here? I need terms for these two types of hydraulic transmissions, terms that make it clear which one I'm talking about and that are both correct and not easily misunderstood by the general public and mechanics. Some of my questions are: Is my own terminology at least correct? Why do those guys at McMillin call their transmission "automatic" even though it doesn't shift automatically? How can I talk about such a transmission (hydraulic, not automatically shifting), making it clear that this is not an automatic transmission (like e.g. the GM 4L60) and neither a manual stick-shift transmission? Oh, and the terms should of course be short enough to be used a few times, not a two-phrase description

Thanks a lot for any information,
Gerhard

 

[Fabrico]

The M1 is by no means the only transmission in this catagory. These are commonly referred to as "manual shift automatic transmissions" or "semi-automatic transmissions". Of course "transaxle" can be substituted in place "transmission".

You could make it more specific to that one and call it the "Torqy Corky" [RIP]

 

[gerhardf]

Thanks, Fabrico. So basically, "automatic" means something like "has a torque converter"?

I'm not sure I can get myself to like the "manual automatic" transmission

 

[gerhardf]

Oh, and in case that wasn't clear to everybody: this is meant for a US target audience.

 

[patprimmer]

I think in the past it was clear.

Manual transmissions had a clutch pedal, a gear lever that moved gears or dogs to engage gears, and two parallel shafts with meshing gears on each shaft. These were normally the main shaft and lay shaft, although some transaxles confused that a little with input and output shafts.

Automatics were hydraulic contraptions that had a torque converter, an epicyclic gear train, and a hydraulic valve body to control shifts by application or release of clutches and bands.

Since the advent of electronic controls with full manual override for torque converter/epicyclic gear boxes and paddle shifts, air powered and/or electronic controlled shifts on dry clutch on flywheel, two parallel shaft transmissions, and now CVTs, the terminology is becoming confusing.

I still think of a dry clutch non epicyclic as a manual type gear box, no matter how it is shifted, and a torque converter with epicyclic box as auto type box, no matter how it is shifted.

But then I am 60 years old next year, so my ideas might be old fashioned.

Regards

eng-tips, by professional engineers for professional engineers
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[Fabrico]

I agree Pat, there's a lot more than just the torque converter making things easy.

Gerhardf, keep in mind that the cranky old dry clutch has to be used on each and every shift. In this case, that's done automatically too.

As a twister, a CVT never shifts, is it necessarily an automatic?

In this case, 2 out of the 3 functions a fully automatic trasmission should perform, are fullfilled.

 

[ivymike]

a CVT never shifts... but some of them pretend to, so that the car makes noises that people are familiar with.

 

[patprimmer]

I thought by definition they were constantly and automatically shifting, even if in infinitely small increments.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Warpspeed]

I also concur with Pat.

To me, a hydraulic transmission suggests a hydrostatic drive of some sort. There is usually a hydraulic pump driving a hydraulic motor, with no direct mechanical coupling, only a fluid link with variable positive displacement pumps and/or motors.

So we might have:

1/ Full manual transmission with clutch and conventional sliding gears.

2/ Full hydrostatic drive, no gears at all. Just a control lever with infinitely variable ratio.

3/ Automatic transmission which covers everything else, and really needs to be defined as to exactly what it is.

 

[Fabrico]

On the flip side, Roadranger has their line of automatic shift, standard type transmissions that can be had with or without clutch control. They refer to theirs as "Automated".

 

[gerhardf]

Thanks to all, that was enlightening

I decided to go with Fabrico's first suggestion. I'll call both types "automatic transmissions", and where I need to make a distinction, I add "automatic shift" or "manual shift" as appropriate.

This seems to be clear enough and in line with the general use of these terms.

 

[drwebb]

Not familiar with the Roadranger line, but a mechanically manual transmission with servo-operated clutch and gear selection is commonly designated an Automated Manual Transmission (AMT). Audi is championing its double wet clutch version of this approach, but CVTs (mainly belted variator versions) and 6-speed ATs appear to have carried the day (for now) as alternatives for most passenger cars.

Marketing terms for alternative transmissions to the enthusiast/sporting market is fairly tricky as you point out. For the masses though, I wonder how many Mini, Murano, 500 etc. drivers know or care about their high tech drivetrains?

 

[Fabrico]

The Roadranger line, by EATON/DANA, is one of the oldest and most popular big-rig transmissions in North America. However, most on the road are still manual shift.

If it's not too late, another term is "AutoShift" or a variation of it. It's kind of catchy and can be interpreted different ways. Auto-Shift, AutoButShift

You don't shift volume, electric motor speed, temperature or light levels, you adjust them. At any rate, CVT's have surely stayed in the automatic catagory.

As mentioned by others here, some of these concepts really should be defined and named, if not for the masses, then at least for their intended market.

 

[Warpspeed]

In 1972, Porsche introduced the "sportmatic" transmission, which was a conventional four speed manual transaxle with vacuum actuator for the clutch. It also had a torque converter on the engine side of the clutch. Placing your hand on top of the gear lever sucked in the clutch.

 

[Fabrico]

That clutch sucked alright. I had the same thing in a 1968 Volkswagon. VW called theirs the "Automatic Stick Shift" (A.S.S. believe it or not )

I doubt the McMillins want that distinction.

 

[Warpspeed]

Yeah, the sportmatic was certainly not an improvement. I believe that Porsche lost a lot of sales in the US in the 60's because many Americans took severe fright when they saw that third pedal. Hence the half hearted attempt at building an "automatic" Porsche. Not absolutely sure, but I believe the 928 was the first "real" automatic Porsche.

But it does go to show that there have been some strange variations to the traditional slush box plus torque converter.

 

[Tmoose]

Some manufacturers of high performance parts for US passenger car automatics call their products "manual shift valve bodies" or something similar. The original automatic(?) transmission is Still there, with torque converter, and clutches hydraulically applied using logic based on things like throttle position and rpm, but each gear change requires a command from the driver via lever position.

 

[notnats]

Then what was the "pre-selective" gearbox which I think was popular for a while in the 1930s? I got the impression that the next gear was selected then didn't change until the clutch was depressed.

Jeff

 

[Fabrico]

Then what was the "pre-selective" gearbox which I think was popular for a while in the 1930s? I got the impression that the next gear was selected then didn't change until the clutch was depressed.

The Chrysler "Clutch Flight" from the 50's would do that. It used a hydraulic coupling instead of a torque converter. The shifter was really a range selector. It was pretty handy behind a 331 Hemi for doing burnouts .

 

[JayMaechtlen]

Yes, there were all kinds of kludges intended to make driving easier.
Of course, the first popular american automatic transmission didn't have a torque converter. (GM's Hydramatic)
It was automaticly shifted, epicylic, hydraulicly controlled, etc. It 'made do' with a fluid coupling and a really low first gear.
Dodge had a conventional 3-speed sliding gear trans with dry clutch and flud coupling in series. Was strange to release the clutch pedal in gear and have the engine keep idling with the brake holding it stationary.
Chrysler had some kind of semi-automatic trans also, don't know details.
I'm sure there were many more...
Cheers
Jay

Jay Maechtlen

http://home.covad.net/~jmaechtlen/