input shaft and the other on the driven or output shaft,
plus a cross-shaped unit called the cross (Figure 53-16).
A yoke is used to connect the U-joints together. The four
arms of the cross are fitted with bearings in the ends of
the two shaft yokes. The input shaft's yoke causes the
cross to rotate, and the two other trunnions of the cross
cause the output shaft to rotate. When the two shafts are
at an angle to each other the bearings allow the yokes to
swing around on their trunnions with each revolution.
This action allows two shafts, at a slight angle to each
other, to rotate together.
Universal joints allow the drive shaft to transmit
power to the rear axle through varying angles that are controlled
by the travel of the rear suspension. Because power
is transmitted on an angle, U-joints do not rotate at a constant
velocity, nor are they vibration free.