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.
Source: CDX Global
