The late 904 transmission are indeed lockup but they can be changed to non lockup so easily it's not funny! Knock 1 check ball out of the front pump asembly, change the Input shaft, change the valve body. Done. I have a 300m shaft that I am putting in mine. The front drum asembly is 5 clutches stock not 4 like the early Trans and the forward is 4 clutches not 3 like the early Trans. They make thin checked clutches for the 904 just like the 727 so I have 6 clutches going into my high gear drum. I'm going to give it a shot. I break it, I break it.