A904 vs A999

The A999 has 5 clutches in the front drum and 4 clutches in the rear drum. The A904 has 3 clutches in both the front and rear drum. Not all A999 are a lock-up type transmission. The part number is found on the drivers side just above the pan. The following is years and part #'s for A999. 1974-75 #3681844, 1976-77#4028465, and 1978 #4028878. This info is from the direct connection chassis manual. Other than the part # you cannot physically tell a A904 from a A999. The factory only put A999's behind the 360 engine. Hope this sheds some light on the subject.