View source for Drivetrain

{{short description|Group of components that deliver power to the driving wheels}}
{{Other uses}}
{{Distinguish|transmission (mechanical device)}}
[[File:Transverse engine layout.png|thumb|Engine and drivetrain of a transverse-engined front-wheel drive car]]

A '''drivetrain''' (also frequently spelled as '''drive train''' or sometimes '''drive-train''') or '''transmission system''', is the group of components that deliver mechanical power from the [[prime mover (engine)|prime mover]] to the driven components. In [[automotive engineering]], the drivetrain  is the components of a motor vehicle that deliver power to the [[drive wheel]]s.<ref name="Bosch, Drivetrain" >{{Cite book
  |title=Automotive Handbook
  |year=1993
  |isbn=0-8376-0330-7
  |publisher=Bosch
  |edition=3rd
  |chapter=Drivetrain
  |ref={{harvid|Bosch|Automotive Handbook}}
  |page=536
}}</ref> This excludes the engine or motor that generates the power. In marine applications, the [[drive shaft]] will drive a [[propeller]], thruster, or waterjet rather than a [[drive axle]], while the actual engine might be  similar to an automotive engine. Other machinery, equipment and vehicles may also use a drivetrain to deliver power from the engine(s) to the driven components.

In contrast, the [[powertrain]] is considered to include both the [[automotive engine|engine]] and/or motor(s) as well as the drivetrain.

== Function ==
The function of the drivetrain is to couple the engine that produces the power to the driving wheels that use this mechanical power to rotate the axle. This connection involves physically linking the two components, which may be at opposite ends of the vehicle and so requiring a long [[propeller shaft]] or [[drive shaft]]. The operating speed of the engine and wheels are also different and must be matched by the correct [[gear ratio]]. As the vehicle speed changes, the ideal engine speed must remain approximately constant for efficient operation and so this gearbox ratio must also be changed, either manually, automatically or by an automatic [[continuously variable transmission|continuous variation]].

== Automotive components ==
The precise components of the drivetrain vary, according to the type of vehicle.

Some typical examples:

=== Manual transmission car ===
[[File:2010 09 27 Hannover 161606 (8600786806).jpg|thumb|Rear axle with hypoid bevel gear final drive]]
* [[Flywheel]]
** [[Dual mass flywheel]] ''still rare''
* [[Clutch]]
* [[Transmission (mechanics)|Gearbox]]
** [[Overdrive (mechanics)|Overdrive]] ''Since the adoption of 5 speeds has become standard ''
* [[Propeller shaft]]
* [[Rear axle]]
** [[Final drive]]
** [[Differential (mechanical device)|Differential]]

=== Automatic transmission car ===
* [[Torque converter]]
* [[Transmission (mechanics)|Transmission]]
* Propeller shaft
* Rear axle
** Spool
** Differential

=== Front-wheel drive car ===
[[File:Manual Transmission for Volkswagen Golf.jpg|thumb|Front wheel drive manual transaxle, showing the gearbox and final drive incorporated in the same housing]]
* Clutch
* Motor
** Gearbox
** Final drive
** Differential
** [[Drive shaft]]s and [[constant-velocity joint]]s to each wheel

=== Four-wheel drive off-road vehicle ===
[[File:Antriebsstrang Baumaschine.JPG|thumb|Construction vehicle drivetrain, with permanent all-wheel drive]]
* Clutch
* Gearbox 
* [[Transfer box]]
* [[Transmission brake]]
* [[Propeller shaft]]s, to front and rear
* Front and rear [[axle]]s
** Final drive
** [[Locking differential]]
** [[Portal axle|Portal gear]]

===Final drive===
[[File:Differentialgetriebe2.jpg|thumb|A cutaway view of an automotive final drive unit, which contains the differential]]
The final drive is the last in the set of components which delivers torque to the [[drive wheel]]s. In a road vehicle, it incorporates the [[Differential (mechanical device)|differential]]. In a railway vehicle, it sometimes incorporates the reversing gear. Examples include the [[Self-Changing Gears]] RF 28 (used in many [[List of British Rail diesel multiple unit classes|first-generation diesel multiple units]] of [[British Railways]])<ref>Mann, R. H., ''Diesel Rail-Cars'', Draughtsmens and Allied Technicians Association, 1964, pp 45–50</ref> and RF 11 used in the [[British Rail Class 03]] and [[British Rail Class 04]] diesel shunting locomotives.
In a [[motor vehicle]], the '''powertrain''' consists of the source of propulsion (e.g. the engine or electric motor) and the drivetrain system which transfers this energy into forward movement of the vehicle.<ref>{{cite web |title=Drivetrain Quiz |url=http://carcare.org/car-care-articles/drivetrain |website=www.carcare.org |archive-url=https://web.archive.org/web/20100616015747/http://carcare.org/car-care-articles/drivetrain |archive-date=16 June 2010 |url-status=dead}}</ref>

=== Powertrain ===
==== Definition ====
The powertrain consists of the prime mover (e.g. an internal combustion engine and/or one or more traction motors) and the drivetrain - all of the components that convert the prime mover's power into movement of the vehicle (e.g. the [[automotive transmission|transmission]], [[driveshaft]]s, [[Differential (mechanical device)|differential]] and [[axle]]s);<ref>{{cite web |title=What Does a Powertrain Warranty Cover? |url=https://www.carchex.com/content/what-does-a-powertrain-warranty-cover |website=www.carchex.com |access-date=30 November 2020}}</ref><ref>{{cite web |title=What is a Powertrain or Drivetrain? |url=https://www.whichcar.com.au/car-advice/what-is-a-powertrain-or-drivetrain |website=www.whichcar.com.au |date=22 July 2016 |access-date=30 November 2020 |language=en-au}}</ref> whereas the drivetrain does not include the power source and consists of the transmission, driveshafts, differential and axles.<ref>{{cite web |title=What is a Car Powertrain? |url=https://itstillruns.com/what-car-powertrain-4681370.html |website=www.itstillruns.com |access-date=30 November 2020 |language=en}}</ref><ref>{{cite web |title=What Does a Powertrain Warranty Cover? What is a Powertrain? |url=https://www.autosimple.com/blog/powertrain-warranty/ |website=www.autosimple.com |date=17 August 2017 |access-date=30 November 2020 |language=en}}</ref>

==== Power sources ====
Most passenger cars and commercial vehicles are powered by either an [[internal combustion engine]], [[electric motor]](s) or a combination of the two.

The most common types of internal combustion engines are:
* [[petrol engine]]s
* [[diesel engine]]s
* [[Common ethanol fuel mixtures|ethanol blends]] (such as [[E85]] and [[Common ethanol fuel mixtures#E10 or less|E10]])
* [[liquefied petroleum gas]]

Most purely electric vehicles use batteries for energy storage and are referred to as [[battery electric vehicle]]s.

Vehicles with both internal combustion engines and electric motors are called ''hybrid vehicles''. If a hybrid vehicle includes a charging socket, it is considered to be a [[plug-in hybrid]], while vehicles that do not include a charging socket (therefore relying on the engine or [[regenerative braking]] to charge the batteries) are considered to be [[mild hybrid]]s.

== See also ==
{{cmn|
* {{annotated link|Two-wheel drive}}
* {{annotated link|Four-wheel drive}}
* {{annotated link|6×4 (drivetrain)}}
* {{annotated link|Six-wheel drive}}
* {{annotated link|Eight-wheel drive}}
* {{annotated link|H-drive}}
* {{annotated link|Continuous track}}
* {{annotated link|Hybrid vehicle drivetrain}}, the drivetrain of [[hybrid vehicle]]s
* {{annotated link|Automotive safety}}
* {{annotated link|Driveline shunt}}
* {{annotated link|Electric vehicle}}
* {{annotated link|Electric vehicle conversion}}
<!-- * {{annotated link|Final drive}} -->
* {{annotated link|Giubo}}
* {{annotated link|Gear train}}
* {{annotated link|Internal combustion engine}}
* {{annotated link|Propulsion transmission}}
}}

==References==
{{Commons category|Powertrain}}
{{Reflist}}

{{Powertrain}}
{{Authority control}}

[[Category:Drivetrain| ]]
[[Category:Automotive technologies]]