John:
"John G. Napoli" <john@xxxxxxxxx> wrote:
It also confuses the heck out of your passengers, who can't figure out what
you're doing. Sometimes you are using the clutch, sometimes you're not.
Sometimes you're shifting to accelerate, sometimes you're not. I can only
imagine what it would be like to explain it to a teenaged valet.[Unless you're starting in low range, you wouldn't be using the clutch]
>
> There is no lockup fluid coupling on either Fluid Drive or
> Fluid-Torque Drive as there is on a modern torque converter.
> The only '50's lockup converter I've heard of is the Packard
> Ultramatic.
>
Correct, there is no lockup clutch. However, the nature of a fluid coupling
(as opposed to a torque converter) permits it to effectively lock up once it
reaches a certain rpm. At that point, the entire fluid mass is rotating
around and 'locking' the driven disk to the driver. Fluid couplings have
straight vanes, and just a driver and driven member. Torque converters have
curved vanes and three elements. This is an oversimplification that perhaps
someone can expound upon, but the fluid coupling does act as if it is locked
up.
Now, fluid couplings do not offer any torque multiplication, either. That's
why the early GM Hydramatic automatic transmissions had 4 forward gears -
there was no torque multiplication available to assist in getting the car
off the line - Hydramatics used fluid couplings.[GM Hydramatics after 1961 did use torque converters.]
At the other end of the
spectrum was the GM Dynaflow, that was essentially all torque converter and
no gears. Many, many different combinations were experimented with by the
early automakers as they sought to find the 'best' automatic transmission
design. For better or worse, the auto industry has evolved pretty much
across the board to a torque converter backed by 3 or more gears with a
mecahanical lockup element in the torque converter.[Almost no automatic with a converter and 3 speed planetaries had lockup except for the Packard Ultramatics which used only the torque converter starting out, then locked it out. It did not "shift."]
I've got an old Jaguar saloon (1953, a Mark VII) with a Borg-Warner three
speed automatic. This tranny was very advanced for its day. It has a
torque converter with a mechanical lockup clutch (!). Why? Well, not for
economy as today, but to minimize heat in this air-cooled tranny. The
tranny also starts in second and shifts to third (high) when in normal
(D)rive. Sound familiar?
Was that Packard Prestomatic [Packard did not use a "Prestomatic."made by B-W? If so, it might be the same B-W
unit I have in my Jag.
> The name "Gyromatic" is exclusive to Dodge. Each make had
> their own trade name for the semi-automatic, though the
> technology was the same. Pre-war Chrysler semi-automatics
> were vacuum-controlled and were hence called Vacamatics;
> post-war were hydraulically activated Prestomatics.
>
Yes, you're right. I have been using the Dodge name - quite frankly, I did
not know the Chrysler name. Thank you!
John
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