Third Order Propshaft Speed Related Vibrations

Third Order Propshaft Speed Related Vibrations

Third order propshaft speed related vibrations cause three shakes or disturbances for each revolution of the propshaft. This type of vibration is very rare and will not be present on vehicles that use U-joints exclusively. On standard all-wheel drive vehicles, don't forget that the front propshaft can also cause this same type of vibration. Shift the vehicle in and out of four-wheel drive in an attempt to verify and isolate the concern.

Note: Some vehicles equipped with an automatic transfer case can still have the front propeller shaft rotate in two-wheel drive; however, it will not rotate at the same speed as it normally would in four-wheel drive. Shift the vehicle into four-wheel drive during diagnosis to eliminate the this potential diagnostic problem.

The following diagnostics apply to front and rear propshafts.

IMPORTANT: A component that is out of balance will NEVER cause a second or higher order vibration, only a first order vibration.

Third order propshaft vibrations are usually caused by:

Failed, failing or binding propshaft Constant Velocity (CV) Joints. Remove the propshaft and rotate the CV-joint through its full range of motion while feeling for any rough spots or looseness.
Improper angles of propshafts equipped with Constant Velocity (CV) Joints. Check the vehicle trim height. Look for any suspension or body height modifications which could affect the angle of the CV-joint. Inspect powertrain mounting for looseness also.

The photograph shown below shows a propshaft with CV joints at each end. This is the rear propshaft of a crossover SUV.

Drive axle problems. – click here to diagnose.

This page was last modified Thursday, March 05, 2009 09:02:31 PM