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I look at some cars, such as Renault Captor, and they have gearbox specified as Duplex. does this mean that the car can be driven either through automatic transmission, or manual transmission.

Secondly, I also noticed some gearboxes marked as semi-automatic. Is there a difference between these two gearbox types?

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I'm not aware of any transmissions on the Renault Captur that are called "duplex"... I think the next big automatic for that range will be a CVT.

Usually, "duplex" refers to a manual transmission mostly used in trucks, which consists of two distinct coutnershafts which are selectable. Mack B series and most notable the Eaton-Fuller "Roadranger" series with which I have some rowing time. These transmissions have a selection of main gears, augmented with another whole set of gears; a type of HI-LO arrangement.

This becomes quite intense with triplex and quadraplex gearsets... (the second part of the transmission having LOLO, LO, DIRECT, and HI positions, with as many 5 "main" transmission ratios.) The shift pattern on say a Mack 15, 18, or 20 speed is a work of long practice and mastery, which involves a complex ballet to acheive every possible ratio in perfect ascention or decension. In practice, one could skip a few (especially unloaded) as many ratios were only a small fraction different than their nearest next lower or higher counterparts.

"Semiautomatic" usually refers to a system that allows gear selection without, or with limited use of, a clutch. I once owned a 1950 Dodge Wayfarer with such an arrangement - at the time called the first semi-automatic transmission.

The transmission was a combination of manual and "automatic" elements, much like a modern automatic transmission. However, gear changes were performed manually, not as a result of fluid pressure or RPM.

  • for another "semi-auto" transmission see Wilson pre-selector gearbox and Lanchester cars, also used in Daimler... – Solar Mike Nov 8 '17 at 7:29
  • I think the confusion came from German to English translation. Found out that the correct transmission is dual clutch transmission, which was being wrongly translated as Duplex. After further investigations, found out that DCT can be driven as fully automatic or manual (without the clutch pedal) – maress Nov 8 '17 at 9:26

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