There are many possible causes for driveline failure or vibration. One of the biggest factors in driveline vibration complaints is due to many of today’s vehicles have been reduced in weight by the introduction of advanced plastics, aluminum and carbon fiber materials. The shear mass found in many earlier vehicles that used to absorb many drivetrain vibrations have been significantly reduced in effort to obtain better fuel economy. Couple that with industry introducing better tires and wheels, advanced suspensions, quieter gearing, higher rpm engines, overdrive transmissions, increased speed limits and the demand from consumers for smoother quieter running vehicles. Other factors that contribute to vibration complaints, is the lower quality of component parts due to reduction of manufacturing costs and increased quotas. If you combine all of these factors it becomes clear why the manufacturing process has become more critical and the role of the driveline specialists more complicated.

When troubleshooting a driveshaft vibration its important to view the entire drivetrain system and most importantly, each individual part of the driveline system as a whole. Generally speaking, the U-joint kits are the centers of rotation of most driveshafts and the degree of imbalance or run-out is inherently linked to these components. But it goes further than that, the following is an example of how important it is to straighten and dynamically balance the entire driveshaft as a system. According to the manufacturing tolerances the stub shaft the concentricity of the stub butt to the slip spline is.003” The tube butt to the center drill hole can be .006”. The flange yoke pilot run out can be .004” out of round. The flange face to cross-hole can be .006” per flange. The U-joint kits can vary .002”, some lesser brand u-joints have more than that. The slip yoke spline to cross-hole relationship can be manufactured up to .004” out of round. Even if your driveshaft was made perfectly straight an additional .019” (.003 + .006 + .004 + .002 + .004) of total indicated run out can be introduced to the driveline circuit. This doesn’t even take into consideration the concentricity of tubing, quality of the universal joints or welding tolerances. In addition, the straightest driveshaft in the business can be well out of balance if the distribution of mass is unequal during the manufacturing process. Rough castings that most driveline components are made of rarely have an equal distribution of mass. These examples do show the maximum tolerance range of manufactured components and unknown variables in castings, but in reality it’s actuality quite possible.

This is why DLNW must have all the components used in the vehicle during the building a balance process. More importantly, the basic law of physics spells trouble for an unbalanced driveshaft. As in anything that rotates at a high speed the imbalanced forces are increased by the square of the rpm. When the rpm is doubled, the imbalanced forces are increased by a factor of four. Triple the rpm and introduce an imbalanced force of nine. Quadruple the rpm, and see a factor of sixteen in imbalanced forces. This exponential increase of unbalanced forces is why driveshaft vibrations typically get worse with an increase in speed.