Driveline Failures & Vibrations

Driveshaft Vibrations

Driveshaft vibrations typically fall into four main categories


    Transverse Vibrations:

  • Caused by an unbalanced driveshaft.
  • Occur once per driveshaft revolution.
  • Common causes include shaft damage, missing balance weights, or foreign material stuck to the driveshaft.


    Torsional Vibrations:

  • Occur twice per driveshaft revolution.
  • Often result from excessive U-joint angles or a shaft that is out of phase with its design specifications.
  • A yoke misaligned by just one spline can lead to torsional vibration issues.


    Critical Speed Vibrations:

  • Happens when a driveshaft operates at an RPM exceeding the safe limits dictated by its length, diameter, and mass.


    Component Failure:

  • Vibrations caused by failing components such as U-joints or motor and transmission mounts
    Example: A failing U-joint can create significant vibration.

Driveline Failures

    Shock Load:

  • A sudden force applied to a driveline component, making it the most common cause of failure.
  • Cold temperatures can exacerbate shock load failures.


  • Common scenarios include:
    Driving into an immovable object under power.
    Tires suddenly gaining traction after spinning on a slick surface.
    Attempting to pull an immovable load, such as a trailer with frozen brakes.
    Popping the clutch at higher-than-normal RPMs.


    Excessive Torque Load (Torsional Fatigue):

  • Prolonged force applied beyond recommended specifications.
  • Typically caused by pulling loads heavier than the vehicle’s rating.


    Improper Application:

  • Occurs when driveline components are not suited to the vehicle’s specifications or intended purpose.


    Surface Fatigue (Contact Fatigue):

  • A general term for damage on the load-bearing surfaces of driveline components, which can include:
    Brinelling: Permanent indentations on the surface.
    Spalling: Flaking or cracking of surface material.
    Galling: Material transfer or tearing due to friction.


    Critical Speed:

  • The RPM at which a driveshaft operates beyond safe limits relative to its length, diameter, and mass, leading to instability and potential failure.
Twisted Tubing
  • Shock Load:
    Sudden force applied to the driveline.
  • Excessive Torque Load:
    Prolonged force exceeding recommended specifications.
  • Improper Application:
    Using driveline components not suited for the vehicle or its intended purpose.
Driveshaft, Twisted Tube Damage
Spalling

Spalling, a form of surface fatigue, occurs when the bearings inside the U-joint bearing cap fail to move freely. This results in the bearings grinding against the cross, creating grooves on the surface.


  • Water or Dirt Contamination:
    Infiltration of foreign materials into the bearing assembly.
  • Improper Lubrication Type:
    Use of unsuitable lubricants for the application.
  • Lubrication Failure:
    Insufficient or degraded lubrication.
  • Excessive Load:
    Prolonged exposure to loads beyond the recommended limits.
  • Operation Beyond Maximum Mileage:
    Usage exceeding the specified service life of the components.
Spalling Universal Joint Damage
Brinelling

Brinelling occurs when the bearings inside the bearing cap imprint onto the outer surfaces of the U-joint cross.


  • Continuous Excessive Torque Loads:
    Prolonged force beyond recommended limits.
  • Seized Slip Yoke Splines:
    Preventing the shaft from adjusting in length.
  • Excessive U-Joint Operating Angles:
    Operating at angles greater than recommended.
  • Improper Application:
    Using components unsuited for the vehicle or purpose.
  • Sprung or Damaged Yoke:
    Compromising proper operation.
  • Improper or Insufficient Lubrication:
    Failing to provide adequate lubrication for smooth operation.
Brinelling Universal Joint Damage
Burned Universal Joint

The factors that cause brinelling and spalling can escalate to severe damage, resulting in a burned-out U-joint cross.


  • Lack of Lubrication:
    Insufficient lubrication leading to excessive friction and heat.
  • Improper Maintenance:
    Failure to follow recommended servicing practices.
  • Incorrect Lubrication Type:
    Using a lubricant unsuitable for the application.
  • Improper Application:
    Employing components that are not designed for the specific use case.
Burned Universal Joint Damage
Fractured Yoke
  • Excessive Torque Loads:
    Prolonged force beyond recommended specifications.
  • Shock Load:
    Sudden, intense force impacting the driveline.
  • Improper Application:
    Using components unsuitable for the vehicle or its intended use.
  • U-Joint Failure:
    Malfunctioning U-joints causing additional stress.
  • Improper Installation:
    Incorrect setup leading to compromised performance.
Fractured Yoke Damage
Broken Tang Half Round
  • Improper Bearing Retainer Bolt Torque:
    Incorrectly tightened bolts leading to stress and failure.
  • Improper Installation:
    Incorrect assembly compromising component integrity.
  • Re-Use of the Bearing Strap:
    Using worn or previously stressed straps instead of replacing them.
Broken Tang Damage
Broken Tube Weld
  • Shock Load:
    Sudden force causing stress at the weld joint.
  • Improper Welding Procedure:
    Inadequate technique or materials leading to weak welds.
  • Balance Weights Positioned Near the Weld:
    Improper placement increasing stress at the weld.
  • Excessive Vibration:
    Persistent vibrations weakening the weld over time.
Broken Tube Weld Damage
End Galling

End galling, or galling, is a form of surface fatigue marked by marring or damage on the flat surface at the end of the U-joint cross.


  • Excessive U-Joint Operating Angles:
    Operating beyond recommended specifications.
  • Improper Assembly:
    Incorrect installation leading to stress on the components.
  • Sprung or Damaged Yoke:
    Compromised yoke integrity causing misalignment.
  • Lack of Lubrication:
    Insufficient lubrication resulting in friction and surface wear.
Bent/Sprung Yoke

A sprung yoke, with a bend occurring within the yoke's ears, may appear imperceptible at a glance and is often detected only during U-joint replacement. In such cases, the crosses will not align properly with the holes on both sides of the yoke.


  • Excessive Torque Loads:
    Forces exceeding the yoke's design specifications.
  • Improper Application:
    Using the yoke in conditions outside its intended purpose.
  • Incorrect U-Joint Removal:
    Mishandling during removal, causing damage to the yoke.
  • Improper Operating Angles:
    Operating beyond recommended angles, leading to stress.
  • Thrown Driveshaft:
    Sudden ejection of the driveshaft causing physical damage.
  • Improper Installation:
    Incorrect assembly leading to misalignment or stress.
  • Poor Maintenance:
    Neglecting regular maintenance, contributing to wear and damage.
Fractured Spline
  • Shock Load:
    Sudden, intense force causing stress and breakage.
  • Excessive Torque:
    Forces exceeding the spline's design limits.
  • Improper Application:
    Using the spline in unsuitable conditions or beyond its intended purpose.

Additional Resources