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Although double clutching is a testing requirement when obtaining a commercial driver's license in some jurisdictions, many truckers learn to shift gears without using the clutch. This is known as floating gears or float shifting, with the clutch needed only during starting and stopping.
Double-clutching: releasing the clutch in neutral to synchronize the speeds of the shafts within the transmission [7] Float shifting: shifting without using the clutch; In big rigs and semi-trucks, the driver may have to complete 24 or more gear changes when accelerating from a standstill to 70 mph (110 km/h).
For example, the Fortschritt ZT 300 has an Unterlastschaltstufe ('shifting under load') function, which needs to be pre-selected by the driver and then activated by pressing the clutch halfway down. This engages the second clutch, which applies a reduction gear to the driven wheels without any interruption in the torque transmission to the wheels.
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.
To double-clutch while downshifting: depress the clutch pedal and move the gear lever to neutral, release the clutch pedal, "blip" the throttle to speed up the layshaft to increase the rotational speed of the lower gear, depress the clutch pedal again, move the gear lever to the lower gear, then release the clutch pedal. Heel-and-toe shifting ...
A direct-shift gearbox (DSG, German: Direktschaltgetriebe [1]) [2] [3] is an electronically controlled, dual-clutch, [2] multiple-shaft, automatic gearbox, in either a transaxle or traditional transmission layout (depending on engine/drive configuration), with automated clutch operation, and with fully-automatic [2] or semi-manual gear selection.
An American-Iranian journalist who once worked for a US-funded broadcaster is believed to have been detained in Iran, according to his former employer and multiple press freedom groups.
Float shifting can reduce clutch wear because it is used so much less (only for starting from a standstill). Conversely, improper engagement of a gear (when the engine and transmission speeds aren't matched) can cause wear on the synchros and lockouts, and damage the gears by physically grinding them together due to a difference in speed.