A dynamic joint communicates rotation between two parts or shafts. The longitudinal axes of the respective parts may be angled relative to one another during rotation and, while torque is being applied. A sealing boot is mounted over the dynamic joint at one end, and to a shaft at an opposite end, to seal lubricant within the joint and to exclude debris and moisture from entering the joint. Known seal boots are fixed, such as by clamping about the shaft and the dynamic joint body, to preclude relative axial movement of the shaft and boot and to prevent ingress of contaminants into the joint and egress of lubricant from the joint.
Under high power, high torque and other high performance applications that may occur in racing, towing or off-road usage, for example, the dynamic joint may experience a significant increase in temperature as a result of the power being transferred therethrough. The temperature increase of the joint will also increase the lubricant temperature and the ambient temperature within the sealing boot resulting in a pressure differential between the interior and the exterior of the boot. The increase in temperature and pressure may cause the boot to swell until the pressure acting on the interior of the boot overcomes the clamping force exerted about the shaft and/or the dynamic joint body. When the clamping forces are overcome, high pressure, high temperature gas is expelled from within the sealed boot, usually by bypassing the clamps on the shaft or dynamic joint body (catastrophic venting). Lubricant may also be expelled with the expelled gas.
Upon cooling of the joint, a negative pressure differential is created between the interior and the exterior of the sealing boot causing air to be drawing into the boot in the same manner. Contaminants and moisture may accompany the air as it is drawn into the boot resulting in durability concerns for the dynamic joint. Additionally, the expelled lubricant is not replaced which also may result in reduced durability of the dynamic joint. On the other hand, if the clamping force is high enough, air may not re-enter the boot causing it to collapse on the dynamic joint which can damage the joint during subsequent operation of the vehicle.