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Re: Ultramatic
#21
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humanpotatohybrid
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Kevin that is correct EXCEPT direct will engage in Low or High gear. But the speed is no different, so unless you stay in Low up to a real good speed, you'll never feel it. This is true in ALL Ultras 49-56. To be clear, this does not happen in Drive on the Twin Ultras. Those go from Low Converter -> High Converter -> High Direct with no exception except if you floor it in High Direct you will drop down to Low Converter in one operation, referred to as Kickdown.

"53", these questions can be easily answered by referencing the charts and the Ultramatic manual.

In short, the direct shift throttle valve compares the force applied by the throttle valve output pressure on one end and the governor output pressure on the other. For most intents and purposes, the throttle valve pressure is proportional to throttle opening, and the governor pressure is proportional to car speed. When you're off the throttle, the governor pressure will exceed the throttle pressure against this valve once you hit about 15 MPH. At full throttle, about 35-40 MPH; and at kickdown (= "full throttle plus") it's 50 MPH. The same is true when slowing down: imagine you're heading up a hill at moderate throttle and losing speed. You want the torque converter to kick back in, and the more throttle you need, the sooner (higher speed) you want this to happen so you get both more torque (from the converter) and more engine speed (as to not lug the engine) sooner rather than later. Of course this equates to more power overall; such is the "magic" of the converter on an automatic transmission.

Posted on: 6/17 15:57
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Re: Ultramatic
#22
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53 Cavalier
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Thank you, I hadn't come across the charts before. Little by little I get a better understanding of how my transmission works. Emphasis on little! LOL

Posted on: 6/17 16:12
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Re: Ultramatic
#23
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HH56
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Actually there is direct drive in low range as this bit from the training manual explains. DD is engaged by a combination of throttle pressure and governor pressure working against and then with each other. If you want you can check the training manual for the full sequence and explanation of which valves and pressures are involved in determining when DD is engaged.

One common misconception on the original Ultras is an actual shift occurring. This is not the case and a real shift as commonly described from first to second to direct did not happen until the 54 gear start later renamed the Twin Ultramatic came along. On the original 49 thru late 54 Ultras, once high range or low range is selected it stays in that gear and relies on torque multiplication in the converter for most of the work. Going into DD is not an actual shift but is rather a clutch coming in which locks the converter pump and driving turbine together to make the converter in effect one straight piece of metal between the engine and trans.

Attach file:



jpg  Ultra.jpg (230.01 KB)
209_6670a6b5e199e.jpg 2418X918 px

Posted on: 6/17 16:13
Howard
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Re: Ultramatic
#24
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53 Cavalier
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I had the same misconception and was why I couldn't make sense of the shift pattern of my car. It was like there was something missing.

Posted on: 6/17 16:17
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Re: Ultramatic
#25
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kevinpackard
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Quote:

humanpotatohybrid wrote:
Kevin that is correct EXCEPT direct will engage in Low or High gear. But the speed is no different, so unless you stay in Low up to a real good speed, you'll never feel it.


This explains why I assumed no direct drive in Low gear. I've never taken it up to the speed of direct drive engagement in Low gear. Thanks for clearing that up!

-Kevin

Posted on: 6/17 18:35
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