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by Tondoteottotote on February 8th, 2005

Tondoteottotote

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Why do most 18-wheelers have manual transmissions instead of automatic transmissions?

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  • by dieselfool on August 8th, 2006

    dieselfool

    Working the trucking industry, I've seen alot of both transmissions. There are actually two different types of automatic transmissions for semi trucks. One type is fully automatic just like a car and only has a brake and fuel pedal. The other has a clutch pedal that you use for starting out and stopping but shifts on its own once you get going, called under one name as an Eaton Autoshift. Also if you have ever driven either of the automatics, you will notice that a transmission ECU will adjust the engine RPM to get it to go into gear. Ben91069 touched on it, were a semi transmission does not have a gear sychronizer, so engine speed has to be the same as drivetrain speed to shift smoothly. It is the same basic shifting as in a manual transmission. Some people use the double clutching method, but more and more people inclucing myself, "float the gears" where you shift based on rpm without clutching at all. I have also heard drivers say that manual tranmissions are better for mountain driving and heavy haul but they are both out there in the trucking industry. One is not better than the other and both have a purpose, manual is just more popular.

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