Re: Ultramatic
Posted by HH56 On 2024/6/17 16:13:51
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:
Ultra.jpg (230.01 KB)
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:
Ultra.jpg (230.01 KB)
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