You don't necessarily need kick-down capability, but you certainly need to seal that hole. If you don't need/want kick-down, you'll have to drop the tranny pan and remove that wire so that you can seal the hole. I used to know the size of plug you need for the hole, but old-timer's is kicking in and I'm not remembering. I'm sure crosley or jakeshoe or one of the other pros can tell you. If your driving style could make proper use of kick-down, then yes, you need a cable and sheath. The fitting at the tranny end of the sheath will have an o-ring. It may or may not completely seal. I had to supplement mine (Lokar) with some silicone.