A driveshaft or driving shaft is a device that transfers power from the engine to the point
where work is applied. In the case of automobiles, the drive shaft transfers engine torque
to the drive axle, which connects the two wheels together on opposite sides and with which
they turn. The driveshaft is also sometimes called propeller shaft.
Drive shafts are essentially carriers of torque. Before they became a vogue, older
automobiles used chain drive and even generators to transmit power to the wheels. Drive
shaft today, however, have U-joints, devices which help them to move and down during
suspension. Some driveshafts also have another kind of joint, called slip joints, which
allow them to adjust their lengths to the movement of the suspension.
Adjustments aside, drive shafts are of different lengths depending on their use. Long shafts
are used in front-engined, rear-drive vehicles while shorter ones are used when power
must be sent from a central differential, transmission, or transaxle. Because of the load
they carrie, driveshaft must be strong enough to bear the stress that is required in the
transmission of power. Thus, they must be periodically checked, too. Some U-joints do not
require periodic lubrication as they have been designed that way by their manufacturers,
but they must be inspected at each oil check nevertheless.
Bad U-joints could cause the driveshaft to separate from the vehicle.