Driveshafts may be balanced for higher speed applications. The general rule of thumb is that driveshafts operating 500+ rpm will be balanced. Balanced driveshafts must be rebalanced whenever they are disassembled and reassembled. Universal driveshafts do not work well in combination high misalignment, high speed applications. This is due to the non-uniform angular velocity experienced by the center of the driveshaft between the joints (Cross & Bearings). The angular acceleration resulting from a combination of high angles and high speeds can result in excessive vibration of the center section. Constant velocity joints are better suited to this type of application. DO NOT INTERCHANGE CONSTANT VELOCITY JOINTS WITHOUT CONSULTING KOP-FLEX ENGINEERING.