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Parts and Operation: Dynaflow

General Motors produced multiple-turbine torque converter transmissions from 1954 to 1961, including the Twin-Turbine Dynaflow and triple-turbine Turboglide, which shifted within the torque converter rather than through pressure valves. By the late 1960s, most fluid-coupling multi-speed transmissions had been replaced with more efficient 3-speed units incorporating lock-up torque converters to improve fuel economy. As computer control replaced mechanical systems, transmissions adopted solenoid-controlled shifting for more precise shifting and adaptation to individual driving styles. Automakers have increasingly added gears, with ZF Friedrichshafen introducing the first 6-speed in 2002 and Mercedes-Benz debuting the first 7-speed

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302 views1 page

Parts and Operation: Dynaflow

General Motors produced multiple-turbine torque converter transmissions from 1954 to 1961, including the Twin-Turbine Dynaflow and triple-turbine Turboglide, which shifted within the torque converter rather than through pressure valves. By the late 1960s, most fluid-coupling multi-speed transmissions had been replaced with more efficient 3-speed units incorporating lock-up torque converters to improve fuel economy. As computer control replaced mechanical systems, transmissions adopted solenoid-controlled shifting for more precise shifting and adaptation to individual driving styles. Automakers have increasingly added gears, with ZF Friedrichshafen introducing the first 6-speed in 2002 and Mercedes-Benz debuting the first 7-speed

Uploaded by

Gary M Trajano
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© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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General Motors produced multiple-turbine torque converters from 1954 to 1961.

These included the


Twin-Turbine Dynaflow and the triple-turbine Turboglide transmissions. The shifting took place in the
torque converter, rather than through pressure valves and changes in planetary gear connections.
Each turbine was connected to the drive shaft through a different gear train. These phased from one
ratio to another according to demand, rather than shifting. The Turboglide actually had two speed
ratios in reverse, with one of the turbines rotating backwards.
By the late 1960s, most of the fluid-coupling four-speed and two-speed transmissions had
disappeared in favor of three-speed units with torque converters. Also around this time, whale
oil was removed from automatic transmission fluid.[4] By the early 1980s, these were being
supplemented and eventually replaced by overdrive-equipped transmissions providing four or more
forward speeds. Many transmissions also adopted the lock-up torque converter (a mechanical clutch
locking the torque converter pump and turbine together to eliminate slip at cruising speed) to
improve fuel economy.
As computerized engine control units (ECUs) became more capable, much of the logic built into the
transmission's valve body was offloaded to the ECU. Some manufacturers use a separate computer
dedicated to the transmission called a transmission control unit (TCU), also known as the
transmission control module (TCM), which share information with the engine management computer.
In this case, solenoids turned on and off by the computer control shift patterns and gear ratios, rather
than the spring-loaded valves in the valve body. This allows for more precise control of shift points,
shift quality, lower shift times, and (on some newer cars) semi-automatic control, where the driver
tells the computer when to shift. The result is an impressive combination of efficiency and
smoothness. Some computers even identify the driver's style and adapt to best suit it.
ZF Friedrichshafen and BMW were responsible for introducing the first six-speed (the ZF 6HP26 in
the 2002 BMW E65 7-Series). Mercedes-Benz's 7G-Tronic was the first seven-speed in 2003,
with Toyota introducing an eight-speed in 2007 on the Lexus LS 460. Derived from the 7G-
Tronic, Mercedes-Benz unveiled a semi-automatic transmission with the torque converter replaced
with a wet multi clutch called the AMG SPEEDSHIFT MCT.[5] The 2014 Jeep Cherokee has the
world's first nine-speed automatic transmission for a passenger vehicle to market.

Parts and operation[edit]

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