Driveshaft Vibrations

There are generally four types of driveshaft vibrations.

  • Transverse Vibrations – are typically the result of an unbalanced driveshaft. A transverse vibration will occur once per every revolution of the driveshaft. This could be because of damage to the shaft, missing balance weights or foreign material stuck to the driveshaft.
  • Torsional vibrations – occur twice per revolution of the driveshaft. They could be due to excessive u-joint angles or a shaft not in phase with its design specifications. A yoke outside of its design phasing by just one spline can cause torsional vibration issues.
  • Critical speed vibrations – occur when a driveshaft operates at an RPM too high in relation to its length, diameter and mass.
  • Component failure – of the driveshaft or the motor and transmission mounts can cause vibration. A failing u-joint is a prime example.
Driveline Failures

There are many different causes behind the failure of various driveline components. A few of these can be the cause of failure for multiple components of a driveshaft. The following are key terminology to common driveline failures.
Shock Load is a sudden force applied against a driveline component. It is also the most common cause of failure. Extremely cold temperatures can facilitate a failure due to shock load. Several often seen causes are:

  • Driving into an immovable object under power
  • Tires that suddenly grab after spinning on a slick surface
  • A sudden attempt at pulling an immovable load, such as a trailer with frozen brakes
  • Popping the clutch at higher than normal RPM

Excessive Torque Load, also known as torsional fatigue, is a prolonged force applied against a driveline component at greater than recommended specs. Excessive torque is usually the result of pulling a heavier load than rated for the vehicle.

Improper Application is where the driveline components installed are not in-line with the vehicle specs or its purpose.

Surface Fatigue or contact fatigue, is a general term for several different damage types that can manifest on the load bearing surface of driveline components, including:

  • Brinelling
  • Spalling
  • Galling

Critical speed is the point at which a driveshaft operates at an RPM too high in relation to its length, diameter and mass.

Twisted Driveshaft Tubing

Twisted Tubing

Causes:

  • Shock load
  • Excessive torque load
  • Improper application

End Galling

End galling, or galling, is a type of surface fatigue that is characterized by marring on the flat surface at the end of the u-joint cross.

Causes:

  • Greater than recommended u-joint operating angles
  • Improper assembly
  • A sprung or damaged yoke
  • Lack of lubrication
U-Joint End Galling

Spalling

Spalling, another type of surface fatigue, occurs when the bearings inside of the u-joint bearing cap do not move freely. This in turn causes the bearings to grind against the cross, wearing grooves across the surface.

Causes:

  • Water or dirt contamination
  • Improper lubrication type
  • Lubrication failure
  • Excessive load over a prolonged duration
  • Operation above maximum mileage specifications
U-Joint Brinelling

Brinelling

Brinelling is the result of the bearings inside of the bearing cap stamping into the outsides of the u-joint cross.

Causes:

  • Continuous excessive torque loads
  • Seized slip yoke splines that do not allow the shaft to adjust in length
  • Greater than recommended u-joint operating angles
  • Improper application
  • A sprung or damaged yoke
  • Improper or lack of lubrication
Burned U-Joint Cross

Burned U-Joint Cross

The same occurrences that cause brinelling and spalling can also cause a higher degree of damage that actually burns out the u-joint cross.

Causes:

  • Lack of lubrication
  • Improper maintenance
  • Wrong lubrication type
  • Improper application
Fractured Driveshaft Yoke

Fractured Yoke

Causes:

  • Excessive torque loads
  • Shock load
  • Improper Application
  • U-joint failure
  • Improper installation

Bent/Sprung Yoke

With a sprung yoke, where the bend is within the ears of the yoke, the bend can be imperceptible at a glance and may only be noticed when replacing a u-joint. When installing the new u-joint, the crosses will not be centered through the holes of the yoke on both sides.

Causes:

  • Excessive torque loads
  • Improper application
  • Improper u-joint removal
  • Improper operating angles
  • Thrown driveshaft
  • Improper installation
  • Improper maintenance
Broken Tang on Half Round Driveshaft Yoke

Broken Tang Half Round

Causes:

  • Improper bearing retainer bolt torque
  • Improper installation
  • Re-use of the bearing strap
Broken Driveshaft Tube Weld

Broken Tube Weld

Causes:

  • Shock load
  • Improper welding procedure
  • Attachment of the balance weights too close to the weld
  • Excessive vibration

Fractured Spline

Causes:

  • Shock load
  • Excessive torque
  • Improper application

For Additional Assistance Refer To Spicer Driveshaft Components Failure Analysis Guide