TH400 leak question

[OUbesto]

I am getting a slight fluid leak that builds up around the speedometer cable where it enters the tranny housing. What's interesting is that there are no drips where the cable actually attaches to the tranny but the red fluid accumulates on the larger round band which is about an inch away from the housing. This round band can be finger turned to a point and then I used a pliers and tried to tighten a little but it doesn't seem to lock down. Since I'm looking at this area from my garage floor while using a floor jack, I can't get a real good look at how the speedo cable secures into the tranny housing. It almost looks like there is a small screw in the metal where speedo goes into tranny housing.

Can anyone tell me how the speedo cable is attached to the tranny housing? Also, any thoughts why the fluid would accumulate by the band and not where it enters the tranny housing?