4.9.1.2 Check Operating Angles
To determine whether vibrations are caused by improper driveline angles, run through
the following routine:
1. Inflate all tires to the pressure at which they are normally operated. Park the
vehicle on a surface that is level both from the front to rear axles. Shift the
transmission into neutral and block the front tires. Jack up a rear drive wheel.
2. Rotate the wheel by hand until the output yoke on the transmission is vertical and
lower the wheel you raised back to the floor. This simplifies measurement later.
Check driveshaft angles in the same loaded or unloaded condition as when the
vibration was noted. It is good practice to try to check driveline angles with the
chassis loaded and unloaded.
3. To measure driveline angles, you can use a magnetic base protractor or an
inclinometer, but the inclinometer is definitely preferred as it measures relative
angles. Good quality electronic inclinometers are not expensive and will quickly
pay for themselves in time saved setting up drivelines. To use the magnetic base
protractor or an electronic driveline inclinometer, place it on the component to be
measured (
Figure 8-56
). Some inclinometers have adapters for attaching to
universal joints and end yokes. A display window will show the angle and the
direction it slopes. Track the measured angles working from the front of the
drivetrain to the rear. A component slopes downward if it is lower at the rear than
at the front. A component slopes upward when it is higher at the rear than it is in
front.
4. Check and record the angle on the main transmission. This reading can be taken
on the end yoke lug, with the U-joint cap removed, or on a flat surface of the
main transmission parallel to the output yoke lug plane. Record your readings on
a sketch of the driveline.
Figure 8-56 - Digital inclinometer.
NAVEDTRA 14050A
8-64