CHAPTER 3 - PART 1 - CHASSIS - TRANSMISSION

MOTOR VEHICLE CHASSIS

The chassis is the motor vehicle's load-bearing structure, which supports the body and the vehicle's other components.

In terms of construction, the chassis includes the following systems: the motor vehicle's transmission, steering mechanism, braking system, running gear, suspension and electrical system.

MOTOR VEHICLE TRANSMISSION

The motor vehicle's transmission comprises all the components that transfer the mechanical energy produced by the engine to the drive wheels, adapting rotational speed and engine torque to the driving conditions.

Depending on how motion is transmitted to the wheels, motor vehicles can have front-wheel drive, rear-wheel drive or all-wheel drive. In motor vehicles with front-wheel drive, the front wheels are the drive wheels; in those with rear-wheel drive, the rear wheels are the drive wheels; and in those with all-wheel drive, motion can be transmitted to all wheels.

The transmission comprises:

• Clutch: connects the engine to the gearbox and allows the engine to be temporarily connected to or disconnected from the transmission. Operating the clutch allows pulling away and gear changes to take place progressively, without jerks or stalling the engine;

• Gearbox: is one of the main components of the transmission and allows the motor vehicle's road speed and direction of travel to be changed. Its role is to adapt the tractive force to the driving conditions and the forces resisting forward motion.

Gears are changed using the gear lever. In automatic gearboxes, changes from one gear to another take place without direct intervention by the driver of the motor vehicle, through the gearbox's own mechanisms;

• Propeller shaft drive: transmits engine torque (turning force) between different transmission components without altering it. Depending on the configuration, it can connect the gearbox to the transfer case, or the gearbox or transfer case to the final drive of the drive axle, when these components do not share a common axis or change position during operation.

• Final drive: receives rotational motion from the propeller shaft, reduces rotational speed and increases the torque transmitted to the drive wheels, transmitting motion to the half-shafts and, in turn, to the wheels;
• Differential: allows the drive wheels on the same axle to rotate at different speeds. This is necessary when cornering because the outer wheel travels a greater distance than the inner wheel;
• Half-shafts: transmit engine torque (turning force) from the differential to the motor vehicle's drive wheels. During operation, they are subjected both to torsion, due to the torque transmitted to the wheels, and to bending, due to the forces acting on the drive wheels.