| The u-joint operating angle is the angle formed by two yokes
connected by a cross and bearing kit. There are two kinds of u-joint angles.
The simple one plane angle found in most installations has
all driveline slope confined to one plane, usually the vertical plane. The other
type of driveline angle is compound angle in two planes. This is found in driveline
designs where offset exists in both the vertical and horizontal planes.
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One Plane Angle Driveshaft's, Side & Top View
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Two Plane Angle Driveshaft, Side & Top View
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High angles combined with high RPM is the worst combination,
resulting in reduced u-joint life. Too large and unequal u-joint angles can cause
vibrations and contribute to u-joint, transmission and differential problems. The
improper u-joint angles must be corrected.
Ideally, the operating angles on each end of the driveshaft
should be equal to or within 1 degree of each other, have a 3 degree maximum operating
angle and have at least 1/2 of a degree continuous operating angle.
RPM is the main factor though in determining maximum allowable
operating angles. As a guide to maximum normal operating angles, refer to the following
chart:
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DRIVESHAFT RPM
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MAX. NORMAL OPERATING ANGLE
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5000
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3.25º
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4500
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3.67º
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4000
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4.25º
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3500
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5.00º
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3000
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5.83º
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2500
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7.00º
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2000
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8.67º
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1500
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11.5º
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When the transmission output shaft centerline and axle input
shaft centerline are parallel, the u-joint operating angle permissible is length
of driveshaft divided by five. Example: A short coupled driveshaft with a 15"
length would be limited to 3 degrees maximum operating angle. A 30" shaft would
be limited to 6 degrees.
When the transmission output shaft centerline and axle input
shaft centerline intersect midway of the driveshaft, the joint angles are equal.
However, due to the change to unequal joint angles during up and down axle movement,
this is a more undesirable condition than parallel centerlines. In this case, the
maximum u-joint operating angle is determined by dividing length of driveshaft by
ten. Example: A 30" driveshaft with intersecting angles would have a 3 degree
permissible operating angle.
CHECKING DRIVESHAFT ANGLES IN THE VERTICAL OR HORIZONTAL
PLANE
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WARNING:
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| Rotating shafts can be dangerous. You can snag clothes, skin,
hair, hands, etc. This can cause serious injury or death. Do not work on a shaft
(with or without a guard) when the engine is running |
Use the following procedure to check driveshaft angles for
proper u-joint operating angles.
1. Inflate all tires to the pressure at which they are normally
operated. Park the vehicle on a surface which is as level as possible both from front
to rear and from side to side. Do not attempt to level the vehicle by jacking up
the front or rear axles. Shift the transmission into neutral and block the front
tires. Jack up a rear wheel.
2. Rotate the wheel by hand until the output yoke on the
transmission is vertical, and lower the jack. This simplifies measurement later.
Check driveshaft angles in the same loaded or unloaded condition as when the vibrations
or noise occurred. Always try to check driveline angles in both loaded and unloaded
conditions.
3. To determine driveshaft angles, a spirit level protractor
or Spicer Anglemaster ® II Electronic Driveline  Inclinometer
is required. On a protractor, when angles are read from 0 degree mark (horizontally
- on the driveshaft) record and use the angle shown. When angles are read from either
of the 90 degree marks (vertically - on the flange) do not record the angle shown
on the protractor since the 90 degree marks must be understood to be the same as
0 degrees on the horizontal plane. Thus, if a vertical reading is 85 degrees, the
angle being measured is 5 degrees (90 - 85 = 5 degrees).
To use the Spicer Anglemaster ® II Electronic Driveline
Inclinometer, simply place the sensor on the component to be measured. A display
module will show what the angle is and in which direction it slopes. We offer Spicer
Anglemaster ® II Electronic Driveline Inclinometer for $300.00.
If using a protractor, all angles should be read within
0.25 degree and they should be measured with the  protractor held plumb
on a clean flat surface. The Spicer Anglemaster ® II Electronic Driveline Inclinometer
is automatically accurate to within 1/10 of 1 degree. Always measure the slope of
the drivetrain going from front to rear. A component slopes downward if it is lower
at the rear than 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 bearing assembly removed
or on a flat surface of the main transmission parallel or perpendicular to the
output yoke lug plane. Record your readings on a sketch.
5. Now check the drive shaft angle between the transmission and axle or forward
axle. On short tube length Driveshaft's, check the angle of the driveshaft on
either the tube or slip yoke lug with the bearing assembly removed. On long
tube length Driveshaft's, measure the angle on the tube at least 3" away
from the circle welds or at least 1" away from any balance weights. Be
sure to remove any rust, scale or sound deadening compounds from the tube to
obtain an accurate measurement.
6. Check the forward axle input yoke angle by removing a bearing assembly and measuring
the angle on the yoke lugs or on a flat surface of the angle housing parallel or
perpendicular to the input yoke lug plane. 
7. If applicable, measure the output yoke angle of the forward axle, the angle of
the tandem driveshaft between the forward axle and the rear axle, and the rear axle
input yoke angle.
With all of the angles recorded, complete a drawing as shown
below. There are no u-joint operating angles in your drawing at this time, jut the
slope of the components and their direction. To determine u-joint operating angles,
simply find the difference in the slopes of the components.
When the slopes are in the Same direction on two
connected components, Subtract the smaller number from the larger to find
the u-joint operating angle. When the slopes are in the Opposite direction
on two connected components, Add the measurements to find the u-joint operating
angle.
Now compare the u-joint operating angles on your drawing
to the rules for ideal operating angles mentioned above.
 click image to enlarge.
CORRECTING U-JOINT OPERATING ANGLES
The recommended method for correcting severe u-joint operating
angles depends on the vehicle suspension or driveline design. On vehicles with leaf
springs suspension, thin wedges called axle shims can be installed  under the leaf springs of single
axle vehicles to tilt the axle and correct u-joint operating angles. Wedges are available
in a range of sizes to change pinion angles. On vehicles with tandem axles, the torque
rods can be shimmed. Torque rod shims rotate the axle pinion to change the u-joint
operating angle. A longer or shorter torque rod may be available from the manufacture
if shimming is not practical. Some torque rods are adjustable.
As a general rule, the addition or removal of a 1/4"
shim from the rear torque arm will change the axle angle approximately 3/4 of a degree.
A 3/4 of a degree change in the pinion angle will change the u-joint operating angle
about 1/4 of a degree.
Always take the time to call the vehicle manufacturer if
there are unusual u-joint operating angle problems.
WHAT CAUSES U-JOINT OPERATING ANGLES TO CHANGE
- Suspension changes caused by: worn bushings in the spring
hangers, worn bushings in the torque rods incorrect airbag height
- Revisions in components of the driveline
- Stretching or shortening the chassis
- Adding an auxiliary transmission or transfer case in the
main driveline
- Worn engine mounts
- Raising or lowering of the vehicle
DRIVESHAFT BRAKE
When a driveshaft brake is used, care must be taken to see
that the brake drum is properly piloted, runs true and is in balance.
Other Driveline related issues:
Driveline Trobleshooting
Driveline Field Problems
Driveline replacements
We offer a complete line of accessories for your vehicle, check out the following links:
In addition to differential repair parts we offer free technical support to assist you in solving your automotive problems as well as a large list of the following products to improve your vehicles performance, economy, safety and appearance:
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