Guidelines For Modifying Light Truck Drivelines

Improper driveline modifications were found to influence recent service claims for transmission damage, premature wear-out of U-joints, and noise and vibration. When modifying a driveline use the following guidelines to help ensure proper driveline integrity. Although these guidelines cover the most immediate concerns, they are not comprehensive. The reader is encouraged to further consult the references listed at the end of this bulletin.


In general, limit the amount of balance weight to approximately 3 ounces or less at each end of a shaft. Excessive weight required to balance indicates that the shaft is likely to be distorted beyond the runout specifications and should not be used. Compare the runout of the shaft against the following specifications to determine whether a shaft is worth balancing.

A list entitied "Things-Gone-Wrong" follows. This list contains the "things-gone-wrong" commonly found on vehicles with modified drivelines. Vehicle modifiers are encouraged to use this list to quickly identify problem areas in their build process.