Editing Front-engine, front-wheel-drive layout (section)

==={{anchor|Giacosa|Issigonis|Transverse}} Front-engine transversely mounted / Front-wheel drive===
[[File:BMC Mini 021.jpg|thumb|The [[hood (vehicle)|bonnet]] on this original [[Mini]] is open, showing the transversely mounted engine that drives the front wheels.]]

The first popular transverse engined FWD cars were the DKW 'Front' made from 1931,  which had a twin cylinder two-stroke engine.  
Saab copied this design on their first car, the 1949 [[Saab 92]]. The Trabant in 1957 was also one of the only cars to have a transverse mounted engine, being a sort of DKW successor. This was a novelty, especially for a car being made in a communist country.

[[Alec Issigonis|Issigonis]]'s [[Mini]] of 1959 and related cars such as the [[Austin Maxi|Maxi]], [[BMC ADO16|Austin 1100/1300]] and [[Austin Allegro|Allegro]] had the four-cylinder inline water-cooled engine transversely mounted.  The transmission was located in the sump below the crankshaft, with power transmitted by transfer gears.  Other models that used the "transmission-in-sump" layout included the [[Nissan Cherry|Datsun 100A (Cherry)]] and various applications of the [[PSA-Renault X-Type engine]] such as the [[Peugeot 104]] and [[Renault 14]].   The 1955 [[Suzuki Suzulight]] also introduced a front engine with a transversely installed two-stroke twin-cylinder engine (using DKW technology) in a [[city car]]/''[[kei car|kei]]'' car application, based on the German [[Lloyd (car)#Models|Lloyd LP400]].

[[Dante Giacosa]]'s [[Autobianchi Primula]] of 1964, [[Fiat 128]] and [[Fiat 127]], put the transmission on one side of the transversely mounted engine, and doubled back the drivetrain to put the differential just behind the transmission, but offset to one side.  Hence the driveshafts to the wheels are longer on one side than the other.  This located the weight just a bit in front of the wheels.  It is this system which dominates worldwide at present.

Front-wheel-drive vehicles tend to suffer from ''[[torque steer]]'' under heavy acceleration.<ref>{{Cite web|url = http://www.cnet.com/news/what-the-heck-is-torque-steer-abcs-of-car-tech/|title = What the heck is torque steer?}}</ref> This is caused by differing drive shaft lengths which in turn results in different incident angles at the joints of the driveshaft.  The farther these joints are articulate, the less effective they are at delivering torque to the wheels.

====Front-wheel drive design characteristics====
<gallery>
File:Renault 4 earlier grill 845cc 1967.JPG|'''Mid-engine, front-wheel drive''' ([[Mid-engine, front-wheel-drive layout|MF layout]]): [[Renault 4]] mid-engine, front-wheel-drive layout allows greater distance between front doors and wheelwells, and short front [[Overhang (automotive)|overhang]].
File:AutoUnion (DKW) 1000 (registered 1965) right.jpg|'''Longitudinally front-mounted engine, front-wheel drive''' (FF longitudinal layout): The [[Auto Union 1000]], (today Audi) longitudinal layout superseded the [[DKW F89]]  front transverse engines in the 1950s.
File:Fiat 128 Rally 1972.jpg|'''Transverse front-mounted engine, front-wheel drive''' (FF transverse layout): [[Fiat 128]], followed the footsteps of the [[Autobianchi Primula]].
</gallery>

====Front-wheel drive shafts====

In front wheel drive vehicles, the drive shafts transfer the drive directly from the differential to the front wheels. A short inner stub shaft is splined to the differential side gear and an outer stub shaft is splined to the front wheel hub. Each stub shaft has a yoke, or housing, to accommodate a [[universal joint]], at each end of a connecting intermediate shaft.

Universal joints let the shaft keep rotating while allowing for changes due to suspension movement, such as shaft length and horizontal angle, and shaft angle as the steering turns. Constant-velocity universal joints are normally used to transfer power smoothly between the components. The inner universal can be a plunge or tripod type joint. The tripod is splined to the intermediate shaft and held by a circlip. A ball, supported on needle roller bearings, is fitted to each post of the tripod, and these slide in a trunion inside the yoke. This caters for changes in shaft length and horizontal angle. The drive is transferred through the trunion and balls to rotate the shaft.

The outer universal joint allows greater angular changes but not changes in shaft length. It is normally a ball and cage type with an inner race splined to the intermediate shaft. An outer race is formed in the yoke. The cage retains the balls in location in grooves in both races.
The balls transfer the drive from the shaft to the hub and allow for changes in horizontal angle and for a wide steering angle to be achieved. A flexible rubber boot fitted to each joint retains grease and keeps out dirt and moisture.

Where the differential is not located in the center line of the vehicle, an intermediate shaft can be fitted to maintain equal length drive shafts on each side. This keeps drive shaft angles equal on both sides and helps prevent steering irregularities and vibration.
The outer end of the intermediate shaft is supported by a bearing secured to the transaxle case and a universal joint assists with alignment.
In some cases a longer drive shaft is used on one side. A [[rubber]] dynamic damper may be fitted to absorb vibrations.