904 slow to engage in reverse

All my 727 trans I have modded have exhibited this at some point or another. I use nothing but Transgo kits and a big fan! If I drive daily no issue, but if it sits for more than a few days then I get the TQ drain-back. I always shift to neutral after start to fill the TQ and then it engages just fine if not to harsh. I know it is not a 904 but basically the same deal.