1. Transverse Engine Front Wheel Drive

2. transmits the drive from the gearbox mainshaft (output shaft)
A universal joint fitted to both
ends of the propshaft allows the
engines turning motion to be
sent through varying angles
The Propeller Shaft
transmits the drive from the
gearbox mainshaft (output shaft)
to the final drive pinion,it is made of tubular section to reduce
weight and is balanced to reduce vibration
The distance between
gearbox and rear axle changes
due to suspension movement

3. Universal Joints
A universal joint is a device that can transmit (send) the engines turning effort/motion
(torque) through varying angles.
A shaft which receives its drive
from a Hooke type universal joint,
varies its speed when rotating,
fitting a second universal joint
restores a constant rotational
speed. The vehicles propshaft is
fitted with two Hooke type universal
joints
Front wheel drive
arrangements use a
constant – velocity type
universal joint, as this joint
does not cause a change
in the speed of rotation
(velocity) of the driveshaft
not matter what the angle

4. The Final Drive Rear Axle, Rear Wheel Drive
Front Wheel Drive Transaxle
Before reaching the the road wheels, the engines drive has to pass through the final
drive which is located in the rear axle on RWD vehicles and in the transaxle in FWD
vehicles. Its main purpose is to turn the drive through 90 degrees in RWD layouts and
reduce to the speed of the propshaft or driveshafts (FWD) to a speed suitable for the
road wheels e.g. if the engine flywheel is rotating at 6000 rev/min, this has to reduced
before being passed to the road wheels, which even at 70mph may only be rotating
at 1000 rev/min. The gear ratio provided by the final drive reduces the speed and
increases the engine torque, however unlike the gearbox this ratio is fixed.

5. Transmission/Final Drive/Rear Wheel Drive (Crown Wheel and Pinion)
Bevel gears mesh (contact) at a 90 degree angle
The teeth on the gears may be straight or curved.
Crown
Wheel
Pinion
Straight tooth bevel – the pinion is
fitted on the centre line of crown
wheel, cheap to produce, high
efficiency but noisy. Spiral bevel –
quiet in operation but has high
tooth pressures

6. Transmission/Final Drive/Rear Wheel Drive (Crown Wheel and Pinion)
Hypoid – the pinion is
fitted below the centre
line of the crown wheel,
the propshaft can be set
lower.The pinion is very
strong and quiet in operation.
Special high pressure oil is
required as well as strong
bearings. Hypoid has a low
mechanical efficiency.
Transmission/Final Drive/Rear Wheel Drive (Crown Wheel and Pinion)

7. The Differential
When the car goes round a bend, the inner wheel has to travel a shorter distance than the outer. If both driven wheels were rotated by one solid shaft, they would have to rotate at the same speed, causing the inner wheel to skid, resulting in excessive tyre wear and poor handling. To prevent this, the drive from the engine is divided by the differential between two halfshafts or driveshafts. Each shaft is driven independently by the differential,so as the inner wheel slows, the outer speeds up, one disadvantage of the this arrangement is that if one wheel looses grip and just spins, the other will not be driven,possilby leaving the vehicle unable to move
The Outer Wheel Travels A Greater Distance

8. Operation Of The Differential
When travelling in a straight line, equal
force is applied to both sun gears(which
drive the half shaft/drive shafts) by the
planet gears, which rotate with the crown
wheel, but do not turn on their own
pivots. When cornering equal force is still applied to both sun gears, but to allow
for the change in speed and distance
the inner wheel has to travel, the planet
gears start to turn on their own pivots
and rotate around the sun gears.
Operation Of The Differential