Re: Ultramatic by Borg-Warner?

Posted by 55PackardGuy On 2015/1/20 1:18:23

Quote:

Hope this helps explain what is going on.

Yeahhh, I think so.

Taken from your last post and an earlier one you made, I think these two quotes together give me a better understanding:

"Without the lockout the converter will slip with higher power loss than a torque converter with lower blade angles."

"The lock up clutch is there because the only way to handle the low efficiency of the unit was to use sharper vain angles"


I will rephrase them this way:

"Without the lockout (clutch) the converter will slip with higher power loss at increased speeds than a torque converter with lower blade angles."

"The lock up clutch is there because the only way to handle the low efficiency of the unit at low ("breakaway") speeds was to use sharper vain angles."

(I don't know quite why the Ultramatic "unit" itself was "low efficiency" to start out with, but I can live without that... probably has something to do with sun gears, or solenoids, or something else that's part of the graduate level course.)

So anyway, as I understand it, the Ultramatic vs the Powerglide gives "faster breakaway" because its sharper vain angles give it better torque at low speeds, but these sharp vain angles are not efficient at high speeds, hence, use a clutch at higher speeds.

I would expect that the sharper angle blades would become less efficient at higher speeds for the same reason that boat propeller blades with a steeper "pitch" give good torque off the line but start to cavitate (lose efficiency) as the boat speeds up. Whether it's water or ATF, flailing around in a churning liquid isn't efficient.

BTW, we used to call Powerglides "Powerslides" and Hydramatics "Slidramatics" although the Hydramatics were definitely better. That is, they were better for normal driving. Back in those days, Powerglides were often said to be the transmission of choice for dragsters that used automatics. Don't ask me how or why. (If we start talking about "stall speed" and stuff I'll probably go cross-eyed.)

It's interesting how many different ways automatic transmissions have been configured to do what they do. I seem to remember the Buick "Switch Pitch" torque converter was around for quite a while after the Dynaflow was history. Into the mid-'60s I believe.

The best automatic I've experienced in one of my own vehicles was a plain old 3-speed OD in my '96 Dodge Dakota. I knew WHEN it shifted, WHY it shifted, and I had decent control over HOW it shifted using only the accelerator. I could even feel it downshift firmly into second and first when slowing down to a stop. It wasn't rough, but you could feel it. I don't even know what Chrysler Corp. called it. It had to have had some computer controls, but they seemed to work very well, and the feeling was not that different from a good vacuum/accelerator controlled unit.