Subject: Automobile Engineering

Topic: Transmission Systems, Live Axle & Differential

Difficulty: Low

The transmission system consists of a clutch , a gearbox (also called transmission), giving four, five or even six different ratios of torque output to torque input, a propeller shaft to transmit the torque output from the gearbox to the rear axle & a differential gear to distribute the final torque equally between the driving wheels.

The functions of a transmission system are:
1) To disconnect the engine from the road wheels when desired.
2) To connect the engine to the driving wheels without shock.
3) To vary the leverage between the engine & the driving wheels.
4) To reduce the engine speed permanently in a fixed ratio.
5) To turn the drive through a right angle.

The various components which perform these functions are :
i) Clutch -Its purpose is to enable the driver to disconnect the drive from the road wheels instantaneously & to engage drive from the engine to the road wheels gradually while moving the vehicle from rest.
ii) Gearbox (Transmission): The gear box or the transmission provides the necessary leverage variation between the engine & road wheels.
iii) Bevel pinion & Crown wheel : They turn the drive sound through 90 degree & also provide a permanent reduction in speed. The permanent reduction is necessitated because of the fact that speed of the engine has to be maintained at optimum level at all times, yet a minimum value of torque has to be made available to the road wheels.
iv) Universal Joints : They provide for the relative movement between the engine & the driving wheels due to flexing of road spring.
v) Differential : While taking turns, the driving wheels must turns at different speeds. This is done with the help of differential.