A fellow racer and freind recently told me of two seperate rr carrier spider gears failures he had. Both coming after he switched to a 75w synthetic gear oil made by a popular gear manufactuer. He's not certain that the synthetic is the cause, but had no problems prior to the change and no problems since the return to conventional gear oil. Both incidents happened while initiating his burn out and the water box being somewhat drier on one side. First he broke a spider gear, and a month later he seized a spider gear to the pin. I will say that he was not using Mobil 1 or Red Line, whether that would of made any difference. Any one with simular experiences? By the way, Jims car is not a Buick but the concern still applies to all racers, so I thought I would post for some insight into this. Thanks Brian