My 904 began leaking pretty badly from the rear seal recently. I went to the parts store to get a new seal, and the parts guy said that a 1972 model 904 and a 1976 904 took a different rear seal. I have a 76 904, but I'm running a driveshaft and yoke from a 72 car. Is the diameter the same on the 72/76, or is that the problem that is causing my leak?