I just rebuilt a 904. I attempted to air test the clutchs. When I applied the air i have a hugh air leak and no clutch activation. The sealing rings on the front pump are new. The gasket between the housing looks to be a poor fit. Is there a difference in front pumps in the early 70s. Are there a difference in gaskets. Thanks for any help.

The pump-to-case gasket is the same from '60-on. There was a sealing ring change in '68 but if the rings fit the shaft they're probably correct. If you installed a later pump with an earlier input shaft the bore diameter is larger and the smaller sealing rings won't seal.

Do you have for/aft end play on the input shaft? If not, it's possible that one of the clutch discs is misaligned and won't let the pump properly seat against the case.