904 Transmission rear seal

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?

I think they are all the same. Just pull yours out and match it up. He might be looking at a 727 and a 904.

The 904 rear seal outside diameter changed in '73, the inside diameter stayed the same.

Thanks! I got up under the car today and cleaned it all up. It was the cooling line connection that was leaking. I had to bend some line, but got it squared away. I think it was just blowing back to the tailshaft from there.

Thanks for the help though!