Leaky transmission

727 with a T/A reverse pattern manual valve body seemed to be leaking @ pan gasket, replaced gasket & pan, made 2 passes then leaked. Chased the leak to a shifter shaft seal, removed trans, then v/b, replaced seal. Noticed there was no gasket between separater plate & trans case, is there supposed to be? Made 1 run, leaked. Ideas, thoughts or any help would be appreciated.