speedo cable oring

for some reason i always thought there was an o ring where the speedo cable ties into the side of the tranny. mine was leaking like crazy and the nut was busted so i took it off an no o ring! is that correct is it just a metal on metal seal? am replacing the cable when it comes in. do i need to put an o ring in it? thanks. :TU:

71 Buick GS Stage 1

 

Matt on the autos there is a seal in the housing held in by a small snap ring. Hope this helps.
Rick