This was many years ago but the principle is still the same. On the Sikorsky S-51 there was installed a constant velocity joint in the tail rotor drive system. This constant velocity joint was exactly the same unit used in the steering and driveline for the front wheels on a GM 6X6 Army truck. The unit with a GM part number cost around $60.00. That same unit with a Sikorsky part number cost around $600.00
