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In 1923, a patent was approved in the United States describing the operation of a transmission where the manual shifting of gears and manual operation of a clutch was eliminated. This patent was submitted by Henry R. Hoffman from Chicago and was titled: Automatic Gear Shift and Speed Control. The patent described the workings of such a ...
With modern drive by wire fuel controls, problems are believed to occur exclusively while the vehicle is under way. General Motors cars of the 1950s with automatic transmissions have the R for reverse at the furthest clockwise position in the rotation of the column-mounted shift lever. L for low position is just adjacent as the lever moves one ...
The Automatic Safety Transmission (AST) was a tangent outgrowth of this work. The AST was a semi-automatic transmission using planetary gears and conventional friction clutch, requiring the driver to use the clutch to shift into or out of gear, but not between the two forward gears. Oldsmobile offered the AST from 1937 to 1939, while Buick ...
If the transmission control unit senses a critical fault during driving, it will activate an emergency operating mode: Upon hydraulic failures, it will stop shifting gears and permanently retain the currently selected gear; if the failure can be pinpointed to one of the internal hydraulic control valves, the transmission will continue shifting but stop using the affected gear(s).
The Ford unit is a six-speed with one clutch acting on reverse, first, third, and fifth gears, and the other used for second, fourth, sixth gears. As the first gear is engaged, the 2-4-6 clutch is disengaged and the second gear cogs are engaged. At the appropriate time, the R-1-3-5 clutch is disengaged and the 2-4-6 clutch is engaged.
Despite the problems of later versions, the transmission worked beautifully under the use conditions it was designed for. Packard's Gear-Start Ultramatic (1954), Twin Ultramatic (1955), and Ultramatic Drive (1956), struggled to reliably automate the low to high gear shift transition.
This nomenclature was also used by Mercedes-Benz with the introduction of the four-speed type-3 automatic transmission. As with the Hydra-Matic, the "L" position was actually 1st and 2nd gears, holding the transmissions from shifting above 2nd gear. In Roto the L position meant 3.50 as first range, changing due to 2.93.
The modern automatic transmission is now able to achieve better fuel economy, reduced engine emissions, greater shift system reliability, improved shift feel, improved shift speed and improved vehicle handling. The immense range of programmability offered by a TCU allows the modern automatic transmission to be used with appropriate transmission ...