[Accelo]

Many of these transfers cases do not have any speedometer seals installed from the factory.
It was ok if they leaked back when, I guess.

I have successfully added seals th the speedometer output.
I would plug it off if you have an electronic speedometer.

In regular speedometers the cable has nothing to do with it leaking or not.
A cap with a seal may help. A screw on thread protector will do nothing.